SilverMax_04

There is a lot in this thread about octane. To help you find what you are looking for, I've listed the different discussions by Post Number:

Post #1: Technical Explanation of Octane Number.
Post #4: What Determines an Engine's Octane Requirements?
Post #6: Octane at Altitude (above sea level).
Post #7: Research Octane Number (RON) in the Rest of the World. Also in #1.
Post #9: Should I Try Regular Gasoline in My Max?
Post #29: Octane Requirement Increase from Deposits
Post #30: Detergent Additives to Combat Deposits
Post #42: Detonation (Knock) Causes Thermal Loading of the Engine.

Don't get bogged down in the details (some of them historic) about Octane Number in this first post, but skim the posts listed above for information you can use.

An Australian posted a thread on the 6th Gen Maxima site and talked about using 98 octane gasoline in his Maxima in Australia. I made a number of comments to him about this gasoline octane not being the same as the octane posted in the USA. I pointed out that he was using a Research Octane Number (RON) while the octane you see posted at all US gas stations is a blend of Research and Motor Octane. You can see my comments on posts #7, #9, and #10 on this thread:

http://forums.maxima.org/oldthread.p...55#post3885555

I did all of the discussion on that thread “off the top of my head,” based on working in the oil industry for 35 years. Now I’ve done a little research and found this more detailed discussion from the February 15, 1988 edition of the “Octane Week” Newsletter. To better help you understand what is being discussed, I've placed clarifying information inside of these { } brackets in the body of this short paper. I’ve also placed the one section of this discussion that requires some knowledge of organic chemistry in these [ ] brackets. You can skip that section and still get quite a bit out of this paper.
SilverMax_04

~~~~~~~~~~~~~~~~~~~
A Review of the Term “Octane Number” by George H Unzelman of Octane Week’s advisory board.

Recently I was asked to explain the difference between Research {R} and Motor {M} octane numbers. A second part of the question was: Why does the industry use (R+M)/2 octane?

In general terms the octane number of a gasoline is a measure of its antiknock quality or ability to resist detonation during combustion. A little history is helpful in understanding the different methods of measuring octane quality.

Not too many years after the discovery of the antiknock characteristics of tetrethyl lead, {the lead used in leaded gasoline -- see the next post to get the full spelling of this word} it became obvious that some yardstick was needed to define the antiknock quality of motor fuel. The octane scale was developed in 1926 by Dr Graham Edgar. Iso-octane was the hydrocarbon selected as 100 octane because it would not knock in the highest compression engine in existence at the time. Normal heptane, on the other hand, was designated as zero octane because it would cause intense knock in a very low compression engine. Mixtures of the two hydrocarbons established the linear scale between zero and 100. For example 20% normal heptane and 80% iso-octane has an octane number of 80. Later, methods were established to extend the octane scale above 100.

The Cooperative Fuel Research (CFR) knock-test engine was developed to determine {gasoline} octane number in the laboratory. It is a single-cylinder engine in which the compression ratio can be adjusted during operation. The knock intensity of the fuel {gasoline} under test is bracketed between standard mixtures of iso-octane and normal heptane or other standard fuels of known octane number.

Two standard ASTM {American Society of Testing Materials} test methods define knock characteristics of motor fuels, by the Research (D 2699) and Motor (D 2700) methods. The Research method correlates with engine antiknock performance at low {engine} speed, while the Motor method correlates with high-speed performance. Both methods employ the same basic laboratory engine under different speed, spark advance, mixture temperature, and intake air temperature conditions.

The Motor method was developed first and was adopted and used extensively by the petroleum refining industry in setting finished gasoline specifications. However, during the 1950’s new refinery processes materially changed the hydrocarbon characteristics of gasoline. The road performance of gasoline no longer matched Motor octane number. Another measure of performance was needed and the Research method became the designating octane quality at the gasoline pump.

Because the Research method is less severe than the Motor method, most gasolines have a higher Research octane. The difference between the two numbers is called sensitivity. [For example a cat-cracked gasoline {component} with a Motor octane number (MON) of 81 and a Research octane number (RON) of 93 has a sensitivity of 12. The sensitivity of gasoline depends on hydrocarbon type and cat-cracked gasoline is “sensitive” because it contains a high percentage of olefins and aromatics. By contrast alkylate and isomerate {other gasoline blend streams} are paraffinic in nature and have little or no sensitivity.]

Sensitivity also relates directly to road octane quality. {Road octane is not defined by a specific lab test, but is the observed performance of gasoline on the road – in actual use in a vehicle on the road.} Following the switch to RON for octane specifications in the 1950’s, oil industry research laboratories worked extensively with instrumented vehicles to determine road octane numbers for the various makes and models. There was almost a frenzy of activity during the so-called octane-race period of the late 1950’s. Detroit auto makers steadily increased compression ratios to achieve superior performance and the oil industry followed with higher octane quality of fuels to match vehicle needs.

Because of the tremendous expense of equipping and operating road test facilities, the oil industry continued to use RON for specifying the octane quality of gasoline at the refinery and at the station pump until 1981. On Sept 4, 1981 the Environmental Protection Agency {EPA} published a notice in the Federal Register to amend unleaded gasoline regulations by substituting (R+M)/2 for RON as a measure of unleaded gasoline octane. Since that time the term “octane number” {at least in the USA} has been accepted as (R+M)/2 unless otherwise designated.

~~~~~~~~~~~~~~~~~
I hope this detailed discussion helps you better understand gasoline octane.

SilverMax_04

For some reason this site will not let me type the word tetraethyl on it. To be certain that you get this word correctly, I will spell it out with spaces between each letter. t e t r a e t h y l

Now in 2007 the site will allow me to type the dreaded word "tet"

20V6

So, it seems like the American continent is using RON+MON/2 and Europe + Asia (and Australia?) is using RON.
BTW Shell in Germany is selling V-Power 100 RON..... that would be a US 95-96oct I guess....
In my car it says : Unleaded fuel only 95 oct. RON minimum.

SilverMax_04

Thought I would expand a little more on what I posted above on gasoline octane while trying to answer this question and also cover some misconceptions about octane. [All octanes are (R+M)/2].

By using high octane gasoline, we are attempting to prevent engine knock. Engine knock is the premature and spontaneous ignition of gasoline. In effect the fuel EXPLODES rather than BURNS, and this results in incomplete combustion, a loss of power and (over time) engine damage. When this happens, you hear an audible "knock" or "ping", sometimes referred to as detonation. Detonation may vary from a faint noise on light acceleration to a constant, deep hammering noise while driving at speed.

Octane requirements are dictated by the following three engine operating factors:
- Cylinder Pressure,
- Spark Advance, and
- Engine Temperature.

Also, engine deposits can affect all of these factors, and produce engine knock where it otherwise would not exist.

Modern engines (like the VQ35) do a good job of controlling the spark advance and to some extent engine temperature. Cylinder pressure is less well controlled and is more dependent on the environment (the engine’s compression ratio, the altitude where you’re operating and the throttle position). But things get real exciting when you go to maximum power output at WOT (Wide Open Throttle). That's when bad things can happen fast. That is typically one of two times when you need maximum gasoline octane to prevent engine knock. The other is lugging your engine when engine temperatures are high.

Anything you do to increase any or all of these three factors will increase your engine’s octane requirement. So, if you put a turbo-charger on you car, you will increase cylinder pressure. If you’re driving a loaded car up a steep grade at high speeds, you will increase the engine’s temperature (but also slowly decrease the cylinder pressure due to ever higher elevation).

Because many OEMs (Original Equipment Manufacturers) are conservative, their stated octane requirement for their vehicles are frequently based on a series of very strenuous tests on the engine dynamometer that are in all likelihood never seen in the real world. In effect they have you driving at WOT (maximum power) for several hours at a time. The last I checked, all Highway Patrols kind of frown on that.

All of this being true, it is also possibly true that the current VQ35 engine (with a 10.3 to 1 compression ratio and advanced engine controls) is operating on the edge of what can be safely done burning regular gasoline. And this even though the owners’ manual says it can be operated on 87 octane regular gasoline – although they recommend premium. The 3.5L VQ engine in the Maxima is among the most advanced in engine technology today (see Wards Automotive 10 Best Engines for more details). The Honda Accord V-6 advertises use of 87 octane regular, but it only has a 10.0 to 1 compression ratio. Because of this, perhaps the VQ is not so close to the edge with 87 octane gasolines. If you do run 87 octane, I recommend that you work to keep these factors above as low as possible (but there's not much you can do about spark advance).

Now I would like to quote from the 2004 Maxima owners’ manual:
"Use unleaded gasoline with an octane rating of at least 87 AKI (Anti-Knock Index). For improved performance . . . use unleaded premium gasoline with an octane rating of at least 91. . . However, you may use unleaded gasoline with an octane rating as low as 85 AKI in high altitude areas [over 4,000 ft] such as Colorado . . ." {goes on to list all or parts of 10 other high-altitude western states}. I will discuss octane and altitude in more detail later on this thread. Then the owners' manual has a comment {with my interpretation}:

"However, now and then you may notice light spark knock for a short time while accelerating or driving up hills. This is not a cause for concern; because you get the greatest fuel benefit {read 'efficiency'} when there is light spark knock for a short time under heavy engine load." Higher efficiency means better gasoline mileage and when you are very close to getting light spark knock, the engine is apparently at its most efficient. {This is engine lab 101 for Mechanical Engineers.}

You’ve probably heard it said that improper engine timing or excessively lean air/fuel ratios will cause engine knock. Well the engine timing impacts the spark advance factor cited above. And the excessively lean air/fuel ratio will increase engine operating temperatures. So both of these statements are true because of their impact on the important three factors.

Some slight misconceptions about octane and gasoline blending;
1) The higher the octane rating on a gasoline the less volatile it is (evaporative qualities) and the slower the fuel burns.
Comment: While this is correct about the slower burning property of premium gasoline, the volatility of premium gasoline (evaporative qualities) is not directly correlated with its octane rating. The volatility of each grade of gasoline is determined in the blending process (and is usually set as high as the applicable government regulations allow for that time of year). This is because the higher volatility components used to blend gasoline are relatively cheap and have reasonable octane characteristics.

2) Most fuel refiners blend fuels for geographic areas and adjust their blends seasonally.
Comment: All refiners blend their gasolines according to strict EPA regulations for their marketing area and the season of the year.

3) These blending techniques compensate for the decrease in oxygen content with an increase in altitude and compensate for volatility during the warmer or cooler seasons.
Comment: It's not the decrease in oxygen content with altitude that's important, but the lower air pressure at higher altitudes. Because of the lower ambient air pressure, the cylinder pressure is reduced versus the pressure at sea level. Thus, it's possible to use a lower octane fuel at higher elevations without engine knock. Generally above 4,000 feet, 85 octane performs better than 87 octane at sea level. Thus, if you transported (via carrier) a vehicle with 85 octane in the fuel tank from Denver to Los Angeles, you would likely have noticeable knock (unless the engine technology compensated, which it might.)

Comment: Volatility is the ability of the fuel to vaporize. In the 1950s "vapor lock" was a common occurrence because the fuel vaporized in the fuel line rather than in the carburetor. With EPA mandated lower volatility gasolines in use today, you no longer see "vapor lock." What you do see is sometimes difficult starting situations in cold weather (particularly when a cold snap is premature). Vapor lock has also disappeared because most vehicles now place the fuel pump in the gas tank. This keeps the fuel line under pressure which prevents vapor lock.

wiggs500

The forum is such a great resource! My brother and I were just talking about the difference in fuel octanes a few hours ago and I log onto the org and look at all the info I find!!

Thanks SilverMax!

SilverMax_04

I live in Colorado Springs where the altitude is about 6,000 feet above sea level. Last June the local paper had a running debate about the "poor quality" 85 octane regular gasoline that was being sold in almost all of Colorado at comparable prices (they said) to the 87 octane regular in the rest of the country. I wrote a letter to the paper discussing this topic, and the paper chose to treat my letter as an Op-Ed article. I understand that some new car salesmen in town have made copies of this article to give to their customers who ask about gasoline for their new vehicles.

Because the topic of this thread is gasoline octane, and because my article was about octane requirements at altitude, I’ll copy that article on this posting, with added explanations in these { } brackets.
SilverMax_04
~~~~~~~~~~~~~~

In a recent letter to the editor, Charles Piper complained that in most of Colorado 85 octane gasoline costs as much as 87 octane gasoline further east. I will attempt to answer this and other complaints. (An exception to this octane discussion occurs with turbo-charged gasoline engines – about 2% of the vehicle population.)

There have been a number of technical studies over many years showing that for most gasoline engines, the octane required for proper operation (no knocking or pinging) decreases about one octane number for each increase of about one thousand feet in elevation. The exact decrease is very specific to each individual engine, but the average of about one octane is a close approximation for most gasoline engines. Most vehicles fall in the range of 0.8 to 1.2 octane per 1000 feet. Thus, a vehicle that needs 87 octane at sea level will most likely only need 82 octane in Denver {5,250 feet} and only 81 octane here {at 6,000 feet}. Yet that vehicle is getting 85 octane in both locations. Looked at another way, 85 octane in Colorado Springs should perform comparably to 91 octane gasoline at sea level in most vehicles.

This physical characteristic of gasoline engines was considered when many of the smaller refineries that supply the inter-mountain West were built and later expanded (and some were also closed – 25 years ago there were 3 refineries in Casper, Wyo., and today there is only one). Not all refineries that supply the Front Range are smaller like the five existing refineries in Colorado and Wyoming. We are also supplied by larger refineries such as the Diamond Shamrock refinery in McKee, Texas and the Phillips refinery in Borger, Texas, both of which make higher octane grades of regular for lower-elevation markets.

Because the smaller refineries lack the economies of scale and do not have the more sophisticated refining units of the larger refineries elsewhere in the country, they cannot cheaply produce the volume of octane needed to blend the octane of all grades of gasoline up to the national standard of 87, 89, and 92 octane. So they produce 85, 87, and 91 octane because it performs quite adequately in most vehicles above 3,000 feet in elevation. In the past Shamrock or Phillips may have entered into a "gasoline octane war" by increasing the octane of their Front-Range regular gasoline to 87 octane in an attempt to increase their sales volumes at the expense of other refiners supplying our area. But in the today's stressful refining situation in which all refineries are running flat-out making all the gasoline they can make, there is no incentive to increase octane costs when you cannot produce any more total gasoline volume.

Piper complains that "most new car manuals state that you should use 87 octane fuel." While most do say that, most vehicles do not have turbo-charged engines (which usually require 92 octane at all elevations), and will perform adequately on 85 octane at elevation. And if you read the manual carefully, many also acknowledge that above 3,000 feet in elevation, 85 octane gasoline is an acceptable fuel.

Why aren't we paying less for 85 octane? When I drive east into Kansas or Nebraska, I usually find that 87 octane costs there are more than the 85 octane I bought here. The Denver boutique gasoline we all must now burn will likely increase the relative gasoline cost along the Front Range versus Kansas and Nebraska (where this special fuel is not required), so this relationship of cheaper regular gasoline here will probably change this summer. (A more complete discussion of gasoline pricing would take up another column.)

Finally, Piper complains that his own vehicle does not perform properly when he "drives up Ute Pass daily" {into the mountains west of town}. I have two suggestions for him (other than buying higher octane mid-grade gasoline): 1) down shift to the next lower gear to reduce the strain on his engine and its likelihood of knocking; and/or 2) from time to time manually add a good grade of fuel-injector cleaner (Chevron's Techron for example) to his gas tank to help remove the deposits in his engine that help promote knocking.

The Author, of Colorado Springs, retired from Amoco Oil in 1998 after 35 years with the company.

~~~~~~~~~~~~~~~~~~~~~~
If you are still reading, you may be interested to know that when the paper had not published my letter (article) and had published other complaint letters on this topic, I sent them an addendum to my first letter the day before they printed the article above (which did not give them time – and they probably lacked space as well) to carry this information. Here is what I said:

I've not seen my detailed letter (yet) and the subject keeps percolating on your "letters" page. On Saturday, Terry Smith opines that if lower octane requirements were true, then "race cars like the ones that race Pikes Peak could use lower octane fuels." Many of those race cars have turbo-charged engines that must have higher octane fuel. Other race cars burn special high-octane "racing fuel" (the cars at Indy don't even burn gasoline). To equate highly tuned, specialized and specially built racing engines to the more common standard production engines like those in most vehicles is misleading.

Finally, the question of what "owners manuals" say about octane requirements for vehicles -- at altitude. Some manuals don't cover the topic of high altitude operation (like my 1999 Dodge Ram). Others are very specific. I will quote from my 2004 Nissan manual: "In most parts of North America, you should use unleaded gasoline of at least 87 AKI (Anti-Knock Index) number. However, you may use unleaded gasolines with an octane rating as low as 85 AKI in high altitude areas (over 4,000 ft) such as Colorado, Montana, New Mexico, Utah, Wyoming, northeastern Nevada, southern Idaho, western South Dakota, western Nebraska, and the part of Texas which is directly south of New Mexico. " Whether your owners manual specifically states this or not, it is an automotive engineering fact that for most engines, they need less octane for high altitudes.

SilverMax_04

Now that I've posted all I planned to say about the different aspects of gasoline octane; I will attempt to answer your post, above.

To get the octane formula exactly correct, you need to add both Research and Motor Octanes together before dividing the result by two. Technically, your formula above is wrong.

Remember the discussion of gasoline sensitivity – the difference between Research and Motor numbers. For most gasolines that I have experience with, this runs about 10 octane plus or minus about 2 octanes. Assuming a sensitivity of 10 for this German Shell fuel, it would probably have an (R+M)/2 octane of 95. Using this same assumption, your minimum of 95 RON gasoline would have a (R+M)/2 ranking of 90 octane. In the US Nissan recommends premium at 91 octane (which is the lowest grade of premium that I have seen marketed here).

Also, remember the discussion in the first posting about "road octane" -- what you actually experience driving with a gasoline in your car. The move in the US to require (R+M)/2 octane was caused because some gasolines with high Research octane numbers did not perform well in the real world. This move was an attempt to get the oil companies to post an octane measurement that correlated better with the real world.

The marketing departments of oil companies in the States were not happy when the government here mandated the use of (R+M)/2 octanes. They were used to quoting the higher Research Octane numbers to help them sell their premium gasolines. (100 or 98 octane sounds better than 91 octane or 93 octane.) So, IMO unless one of these other countries mandates a change in measuring octane, the oil marketers there will continue to use the higher numbers that the Research method gives them to help sell their premium gasoline. When it only costs them about 5 cents more per gallon to make premium and they can collect 20 cents more per gallon when they sell it, they will try to sell as much of it as they can.

At one time, before the final regulation on octane was written, the US EPA was even considering using the more complex formula of (R+M+M)/3. This was considered because of the greater importance some in that agency (and also some in the oil industry) placed on the Motor Octane measurement. History has shown that the current formula works quite well in the real world.

20V6

There is only one thing to say:

SilverMax_04

I've moved my note below from another thread on this site and edited it.

[QUOTE=Jayzmax04]Ok, you do have me wondering....how much difference is there? I know for a fact that when you've run nothing but Super since the beginning, if you put anything less in it, you will feel the difference. I've been broke and done it to my 97 SE.

I guess im wondering, will that difference balance out? Surely a expert in this matter will step up from here..... [QUOTE]
I know a little about this subject. See what I have to say about octane in the thread above.

I would say that if you are currently getting pinging with 91 octane gasoline, you need to put a bottle of Chevron's Techron in your tank to help clean out the deposits in your engine. This is one of the very best products for cleaning modern fuel injectors (and I don't work for Chevron or own their stock). If you do this, the best time is just before an oil change because it has a tendency to increase the viscosity of the motor oil in your pan. The government mandated level of injector cleaner required in gasoline is not sufficient to keep most modern injectors as clean as they should be. I currently add a bottle of Techron just before I plan to do every oil change.

The VQ35 engine is among the most modern available as far as technology is concerned. It has the ability to compensate for differences in octane, and does so fairly rapidly. I doubt that it would take 2 tanks of a different octane gasoline before it "did it's thing" and compensated for the difference. Much of that compensation will be a change in the spark advance, which is why you should stick to premium if you race your Max. I tend to doubt that this change in octane will make much of a difference in the mileage you get with your Max, but you can also check that to see if it does.

Whether you need to burn premium gasoline depends on where you live (the elevation above sea level) and how you drive your car. (See my discussion of octane at elevation above, I won't repeat that here.) If you frequently race or have a very heavy foot, you should definitely burn premium. If you are light-footed and rarely get on it, then either mid-grade or regular will work for you. If you are curious and considering changing grades, I would suggest first going to mid-grade and try a few tanks. If you have any problems with engine knock or less power, you can always go back to premium. If mid-grade works for you, then you can try a tank or so of regular.

A final point here (I don't want to repeat all I said above): The Honda Accord V-6 has a 10.0 to 1 compression ratio and advetises that it can burn regular gasoline, while the Maxima has a 10.3 to 1 compression ratio and recommends premium (but allows 87 regular). Both engines are among the most modern available today (and beat most Detroit iron hands down). Hard to believe that 0.3 can make that much difference in the fuel each engine needs. So try the mid grade first.

Bobo

Not to split hairs, but my 95SE has a compression ratio of 10.0 to 1 and my friend's 1998 Accord V6 has a compression ratio of 9.8 to 1, a differential of only 0.2. I have been running 89 octane the majority of the time since I bought my Maxima new on October 1, 1994, with absolutely no problems. The last few months I have been using premium more often than not as I have been doing a lot of 45-mile round trips. The only time I have ever had a problem with 89 octane gas was about 2-months ago when I filled up with Chevron 89 across the line in Blaine, Washington. Other Canadian drivers complain about using 87 octane bought in the US for various cars.

Are the additives different in Canadian gas? Is the refining process different? I guess what I'm saying is that octane for octane in the lower and mid grades that Canadian gas is better than US gas. I don't think I'm imagining this.

Comments please from the octane guru.

Thanks

SilverMax_04

Guess that means me. I thought that Canada used the Octane Number [(R+M)/2] method, but its been a while since I was there. Thanks for the confirmation. Thus, it appears to be North America vs the rest of the world (RON).

Additive packages in the US vary from company to company, expect the same is true in Canada, but I'm not familiar with Canadian law on the subject. The US EPA has a mandated minimum additive treatment rate (so many parts per million), but I can't remember the exact rate. Suffice it to say, the rate is not high enough to keep modern fuel injected engines (any vehicle bought in the 90's or later) clean. Some oil companies in the States do provide a better treatment rate, particularly in their premium grade, but I can not specifically name them. When I worked for Amoco in the 80's and early 90's they put 50% more Techron (purchased from Chevron) in their premium than in their regular; and they advertised this fact. Recently, I've not seen any oil company advertising their additive treatment rate in any of their gasolines.

During the time when oil and gasoline prices fell, most oil companies cut back on the treatment rate in their fuel (to the EPA minimum) to save money. Gasoline was considered a commodity by many, and so many companies tended to give up on trying to convince people that gasoline was not a commodity.

Every refinery in the world produces slightly different fuels (both gasolines and distillates). I suspect that the Canadian refinery that supplies the stations you frequent makes good quality. Some refineries even end up "giving away octane" (the fuel is higher than specified) in order to meet other fuel specifications. That may be happening to you in Canada. Obviously, the US refinery that supplied the gasoline you bought in the States does not make their gasoline as well as the one in Canada. Chevron does not have a refinery in Washington state, so the gasoline may have been obtained on exchange from one of the 5 larger refineries in the state. (Or Chevron could have barged the product up from their Richmond CA refinery.) Bottom line: you can't generalize about gasoline in the two countries, you need to know the suppling refinery in each case to determine what is really happening.

Akuma2001

will racing fuel (110 octane) yield better performance or is there a limit as to where there isn't anymore performance gains?

SilverMax_04

Racing fuel at 110 Research Octane rating will likely have a higher sensitivity, and so will likely have an (R+M)/2 rating of from 102 to 104.

Once you have a gasoline with an octane that takes full advantage of an engine's capabilities, further increases in octane do not yield any benefits (but do increase your operating cost). The engine (like a racing engine) has to be designed for such a high-octane fuel to see any benefit. The Maxima engine was designed to operate on 91 to 93 octane fuel (96 to 98 RON) and should not show any improvement with a higher octane gasoline.

If you turbo-charged your Maxima, (remember the 3 critical knock factors from Post #3 above) you will increase the cylinder pressure and could then benefit from a higher octane fuel like racing gasoline.

I also remember seeing a post on this site that Sunoco has a higher octane gasoline available at some of their stations in the east. When I last bought Sunoco in S.C., their premium was 93. So I'm not certain where this higher octane fuel is marketed by them.

Recent Update (2008) on Sunoco 94 octane premium. They have stopped making this fuel, just as BP has stopped making Crystal Clear Ultimate Gasoline (93 octane). The many grades of specific gasoline blends for small areas of the country took the large storage tanks that Sunoco and BP used for their unique blend of premium gasoline. So both are no longer available

Akuma2001

At certain stations they offer 94 octane.

20V6

SilverMax 04....
Slightly off topic, but do you know if AVGAS , 100LL, is measured using RON or (R+M)/2? (I know I can't use it in my Max because of the lead will ruin the cat.)

The reason I ask is, when I worked as a pilot in the US we used 100LL (low-lead) on the airplanes, and so do they here in Norway. To me that doesn't make sense since we're using RON for car gas, I thought we would use RON for AVGAS also... or is it the US that uses both measurements?

SilverMax_04

When I last worked in the oil industry (1998) there were two grades of AvGas sold in the USA. 80-87 (this sometimes was called low lead) and 100-130. I believe that the 80-87 grade was being discontinued at that time. Given the high numbers on the 100-130, I'm certain that these are RON. In 1998 they were using lead in both versions. If the 80-87 is gone, the specs may now require low lead content for the 100-130. The octane boost effect of lead is very high for small amounts of lead, and then falls off when more is added. So low lead content will provide the most "octane kick" for very little lead used in the fuel.

20V6

As far as I know 80-87 is gone and the airplanes using that are converted to 87 car gas. 100LL is the current Avgas and 130 is gone as well. However at least here in Norway, 100LL is also phased out. The new fuel is unleaded 98, but I guess it's a different 98 than we get for our cars.

Thank you for all your information!!

SilverMax_04

The 100-130 AvGas was a single fuel with both ratings. I'm not certain exactly what these ratings mean, but suspect they represented the RON for different airplane operating conditions. My memory was that there were very few planes in the 90's that required 80-87 so it was dropped, requiring the remaining planes to buy 100-130 AvGas. My memory was that there are also problems using automotive gasoline in airplanes. This was never an area of petroleum products that I knew a lot about. Amoco only sold AvGas in a few restricted locations. You need someone who worked for Phillips to address these questions. Phillips sold AvGas in many locations.

Ceasars Chariot

iTrader: (16)

thanks silver, very interesting read !!

Ceasars Chariot

iTrader: (16)

silvermax do you think there is any truth to one countries gas being "crap" as some people put it here versus other countries ? New Zealand measures in RON and if I want to continue putting in something equal to chevron 93 back home then im going to be using there 98 here which is not available at every station, but can be found.

i have heard several Kiwi's refer to their petrol/gas as crap gas. Is there any truth to this I wonder ? Is the gas in the US superior to the gas here in NZ ? Any Ideas or thoughts ? Gas is very expensive here, the cheap stuff is 1.30 a liter I believe so 98 is going to cost me.

thanks
c

Bobo

I can't comment on Kiwi gas, but US gas is crap compared to Canadian gas.

CCS2k1Max

iTrader: (2)

Silver, reading this question in R&T, reminded me of traveling overseas a couple decades back where some gas stations had grades ranging from 85 all the way to 95 octane. At the pumps there was a grade selector so you could blend 91 octane by turning the lever to that grade and seeing throught little peep holes w/ vanes how fast the 85 and 95 grade gasolines were being pumped (hell, we drove rental so it was 85 only but I watched the locals do it) . What's your take on this and how well can this be done? (say, pump 1/3rd tank of 87 and then top it off with the other 2/3rds of 93 ending with the "perfect" 91 octane...).

20V6

They still do that here.... you can get 97 octane unleaded... it's simply a mix of 1/3 95oct and 2/3 98 oct. However the peepholes are gone....

20V6

Like I said earlier, in Europe, it says minimum 95 oct. RON on the fuel door on both the VQ20DE and VQ30DE.... I don't know if your's is boosted or something, otherwise 95 should be sufficient (= 90-91 "US" oct.) I've read some tests by several car magazines in Europe and they all claim that the 95 sold in western Europe always is at least 95 oct. usually closer to 96.... I don't think things are worse in New Zealand....
Is that 1.30 Australian or US dollars a liter?
Here it's currently 1.69 USD pr. liter which equals 6.33 USD pr. US gallon!!!

SilverMax_04

Sorry, I've been gone for a while.

Some refineries produce poorer quality gasoline than other refineries. I don't think this applies to all refineries in a country -- New Zeland or any other country. The Canadians think that their gasoline is better than US gasoline. And it may be true that the US refineries supplying gasoline near the border with Canada produce "crap gas" -- but I can't confirm or deny that. I do know that all gasoline sold in the US is not refined here -- some comes from Canada in pipelines and a few tank trucks and some is imported via ocean tanker from Europe of S America. Also, some Canadian gas stations are selling gasoline refined in the US. Venezuela is a big supplier of gasoline to the southern US and Europe supplies gasoline to the upper east coast. California gasoline specs are so stringent that when I retired in '98 there was only one refinery outside of California that could make that gasoline -- the Amoco refinery at Texas City, Texas.

You are basically correct that you will need 98 RON to come close to a US Octane Number of 93. But remember that Nissan recommends (but does not require) premium gasoline of 91 octane. So 96 RON would likely be comparable. I have no problem with running my Max on 89 octane at sea level, which would be about 95 RON.

As I pointed out elsewhere on this thread, some refineries end up "giving away octane" (versus their posted specification) in order to meet other requirements. Try burning some of this lower RON gasoline and see how it performs for you. You can always go back to the higher octane gasoline if there are any problems -- which IMO is not likely.

SilverMax_04

Sunoco on the US East Coast had blend pumps at their stations for years. Don't believe they are doing it any more, but have not been in the North East for many years. They certainly don't do it at their SC stations.

In the 80's almost all refineries produced and shipped three different grades of gasoline. Now most are only making 2 grades -- regular and premium. When they ship mid-grade gasoline to a station, it is "blended" either in the pipes going to the tank truck, or in the tank truck itself. No reason you can't do that yourself in your gas tank.

There are places where (because of local competition) regular is priced particularly low. Thus, the spread between regular and mid-grade may be 15 cents and the spread between mid-grade and premium may only be 10 cents. That is the ideal time to blend into your tank. I like to start with the premium and put a little more than I think is needed for half of the tank. Then pump the regular. It will be a straight arithmetic average of the two octanes. If you want a 50/50 blend, then don't pump any more regular than the volume of premium you pumped.

A one-third to two-third blend into your tank is a bit trickier. Be safe and pump the premium first in the event you did not calculate properly, you will be able to stop pumping the regular. Doing the regular first and you may run out of space in your tank for the calculated volume of premium.

Bobo

SilverMax 04, could you please elaborate further on your comment about not having a problem in your Max in using 89 octane at sea level. I was aware that you could get by with a lower octane at higher elevation, eg. Colorado but never heard about a lower octane at sea level, which is the elevation I live at. More often than not I have run 89 octane, but more recently (the last 4 months I have run premium - 91 or 92, most of the time). Again I have never had a problem running 89 octane in British Columbia and have 58K on my OEM plugs, albeit 80% highway use.

What roughly would be the elevation level you would feel uncomfortable running 89, assuming you left at that elevation?

Thanks

SilverMax_04

Your Maxima is older than my 04, but I suspect it too has a knock sensor. That feature allows you to generally run lower octane gasoline successfully in a Maxima. My owners' manual says that you can run 87 octane in the 04 Maxima at sea level, and I've done so successfully. Remember my earlier quote about a Maxima with knock sensor and 10.3 to 1 compression ratio pushing the limits of a vehicle that can run 87 octane at sea level. But the Honda Accord at 10.0 to 1 advertises it runs on regular. Nissan does not advertise that the Max runs on regular, but it can -- they say so -- and I've done it.

Having successfully run 87 octane, there is no problem at all running 89. In the US, the only location I would even consider worring about running 89 octane would be Death Valley (below sea level). With the knock sensor it would probably work OK -- but I wouldn't push the engine too hard down there.

The only time I've ever heard light engine knock in my Max is on a warm to hot day (temperature) when the engine RPM falls below about 1,800 RPMs going up hill. It may also be there on WOT (full throttle), but there is so much other noise at that time, who can hear light knock?

Having occasional light engine knock (just barely audible) at light load for a brief period of time is not something to worry about. The engine was designed to handle this. This is the first condition I describe above. Engine knock at WOT will be more damaging; so when running lower octane gasoline, resist full throttle acceleration.

I've come across an SAE paper that I forgot I have. Will cover it in the next post here.

SilverMax_04

I have an SAE (Society of Automotive Engineers) paper done by researchers from Shell back in 1997 on “The Octane Requirement Increase (ORI) from Deposits.” It is quite technical, but I will quote key points this paper makes summarizing earlier research on this topic {with my comments in these brackets}:

“Engine knock arises from pressure pulses generated by the auto-ignition {or pre-ignition} of fuel in the end-gas region of the combustion chamber {above the piston and furthest from the spark plug} before the arrival of the flame front originating from spark ignition” {the spark plug firing}.

“Typical values for octane requirement increase (ORI) range between 5 and 10 {octane} numbers, with the most rapid increase in octane requirement occurring during early stages of deposit formation. . . Deposits cause ORI in these different ways:”

- “The volume occupied by deposits increases the compression ratio and thus the octane requirement of the engine. This contributes about 10% to 20% of observed ORI.”
- “Deposits are thermally insulating which leads to an increase in the end-gas temperature inside of each engine cylinder through reduced heat loss during compression, making knock more likely.”
- “Deposits also influence octane requirements through the transfer of heat from one engine cycle to the next, thus raising the temperature of each fresh fuel-air charge during induction into the combustion chamber. . . Modeling of this effect accounts for up to 50% of the total ORI observed”
- “Inlet system deposits have been shown to affect engine octane requirements, but the causes for this are not clear. . . Theories include . . . changing the extent to which fuel is vaporized in the inlet port. Less evaporation would result in less charge cooling and increase knock tendency. Alternately, deposits could provide a source of heat which raises the temperature of the fuel-air charge as it enters the combustion chamber. . . Such effects are less significant in gasolines containing detergent additives which reduce the level of deposits in inlet systems.”

There are other reasons why deposits may cause engine knock; they have not been fully studied. The ones listed above account for most of the causes.

Be certain to read my next post on “Detergent Additives to Combat Deposits.

SilverMax_04

I've said it on other threads, but it’s worth repeating again here, in somewhat more detail. Given the minimal level of fuel injector detergent mandated in US gasoline, you probably need to put a bottle of top-quality fuel injector cleaner through your fuel tank from time to time. The best cleaner are PEA based and include Chevron’s Techron, BG 44-K, and other high-end additives that are PEA based. A “keep clean” dose of these additives runs from 200 to 400 parts per million (ppm) – which few branded gasolines and no unbranded gasolines meet – thus, the reason for a “clean-up” dose of additive. This dose generally results in concentrations of about 2,000 ppm. This treatment rate works well for clean-up but will generally result in oil viscosity changes if used frequently. One dose just before each oil change is usually sufficient, but this rate is also dependent on how frequently you change oil and the deposit propensity of the fuel-engine combination you are running. You probably need to experiment with how frequently you do this to your Max. I change synthetic motor oil every 7,500 miles and find this frequency of clean-up injector detergent works for my Max. Although these PEA additives are only sold to clean deposits from the inlet system and fuel injectors, there are good indications that they also reduce the level of deposits on valves and inside of cylinders.

Bobo

What fuel injector cleaner/additive do you prefer, Silvermax 04? I have some Chevron Techron that I am considering using a few hundred miles before my next oil change. I haven't seen BG44K or Seafoam where I live. The dealer uses a two-part package, BG02, with one being a cleaner and the other a moisture remover - recommended once a year or every 15K, whichever comes first.

SilverMax_04

I use Chevron Techron because:
- Amoco used it in their gasolines when I worked for them. The experts there thought it was the best avilable, back in the 90's.
- The price when it's on sale at local auto supply stores seems quite reasonable.
- My auto expert friend (he knows much more than I do) believes all of these PEA additives are good, so recommends buying by price. For me Techron has been priced right.

I don't know exactly what you mean by "dealer" -- I put the Techron in the tank myself just before pumping gasoline in -- which mixes up the Techron and the gasoline. I also don't know about a "moisture remover." If the gasoline you burn has ethanol blended in it -- many do -- that is all you need to keep the moisture out. The ethanol "sucks up" any moisture in your tank. (This is why they can't ship gasoline containing ethanol in pipelines -- it picks up all of the water that is in the pipeline.) Don't pay extra for this unless your area does not have ethanol in the gasoline (it will be posted on the station pump if it contains ethanol).

Bobo

By dealer, I mean dealership. Does Chevron typically include ethanol in their gasoline?

SilverMax_04

The only way to know is to read each station pump. It must be posted if there is ethanol in the fuel. If ethanol is not posted, then MTBE is most likely in the gasoline in place of ethanol. Both are called oxygenates because of their oxygen content.

Update by SilverMax in 2011: MTBE has not been used as a gasoline oxygenate in the USA for a number of years. It has been outlawed by the EPA. This leaves ethanol as the only legal oxygenate (containing molicules of oxygen in the fuel.) Many stations in the USA now post this on their gas pumps: "May contain up to 10% Ethanol."

Bobo

So, SilverMax 04, which oxygenate do you prefer - ethanol or MTBE? I suspect the short answer is ethanol.

SilverMax_04

I actually don't like either of them.

The science that is being used to justify oxygenates in gasoline is based on the following 1970's engine technology:"
- No oxygen sensor in the fuel or exaust system.
- Carburators rather than fuel injection.
- No computer control of the combustion process in the engine.

Any newer vehicle with these features will not show any improvements (burning cleaner with fewer pollutants) when burning oxygenated gasoline. All of the modern technology compensates for the gasoline -- both with and without oxygenates. So to say that oxygenated fuels "burn cleaner" was only true for vehicles using 1970's technology -- not today's technology.

What does happen with oxygenates in gasoline is that there is less energy per gallon (or per liter) compared with gasoline without oxygenates. Normal gasoline blend components are made up of two atoms -- Hydrogen and Carbon (hydro-carbons). Oxygenates replace some carbon atoms with oxygen atoms, which have no energy. Less energy translates into reduced mileage. Many people can't measure the loss in mileage because there are so many factors that impact gasoline mileage. But science says that less energy per gallon will (in the end) require more gallons to travel a fixed distance.

Today, the only advantage of either oxygenate is that their presence in fuel increases the octane. Putting 10% ethanol into 87 octane regular increases the final octane to about 89. There are other components for blending gasoline that are cheaper per octane/gallon and don't attract water.

The whole operation is a political boon-doggel that is supposed to help the farmers who grow corn, but actually helps big Agri-Bussiness like ADM. Ethanol in gasoline is subsidized by a reduction in the federal gasoline tax, and some states even reduce their state gasoline tax as well. But don't get me started on all of that.

SilverMax_04

I had this question about fuel injector cleaners a while back. For example, Chevron's Techron is a PEA cleaner. Now I have the answer: Techron is Polyetheramine (PEA), probably the best class of additive in that it can clean all of the components, including combustion chambers. Texaco's System 3 is the same formulation. The big problem is that they cost quite a bit more than other additive packages.

CCS2k1Max

iTrader: (2)

Yes, a bit trickier, but it can be done. Anyone who has been pumping gas into their car for a while should have an idea how many gallons to expect to pump. So if you pump 16 or so gallons every time you fill up, it shouldn't be to difficult to pump just 5.25 gallons of regular and top it off with 10.75 gallons plus of super (notice I used 5.25 instead of 5.333 gallons). The idea being that you'd get better mixing/blending by pumping the smaller amount first.

FishyMan

hey cool thread..

regarding fuel injector cleaners, the brands i really see are CHEVRON, STP FUEL TREATMENT, and GUMOUT. I see also diff't scenarios, where some are for higher mileage, or concentrated etc etc. Any ideas?

I am due for an oil change on my other car, and want to run fuel injector, maybe something that is stronger since it is a 15 year old car. Any ideas?

Also, although the chevron one is techron, do you necessarily use it when u put chevron gas? or will mixing it w/ other brands of gas be okay? I assume it is, but just thought i'd ask, since it may be formulated differently?

SilverMax_04

Your questions. I believe most of the "special scenarios" are advertising gimmics to sell product -- ignore them. Gumout is supposed to have a PEA detergent, but I can't verify that. They also have a cheaper one that works well in carburators, but I would not use it for fuel injection.

I would be careful and not put more than the recommended dose of Techron in your tank. Chevron has a bottle that is listed for 20 gallons. They also sell a smaller bottle for 12 gallons. I would dump the appropriate size bottle in your tank and immediately fill it with gasoline to get to either value. Some times "slow and easy" is better than "fast and quick." IMO this is one of them. If the car has never had this treatment before in 15 years, you may want to do a second bottle immediately after the first. I would run down your first tank to about 1/8 of a tank remaining before doing this. Then change your oil after the gas treated with the second bottle is almost gone.

Most oil companies today are putting the minimum amount of detergent in their gasoline, and only a few are using a PEA detergent, Chevron/Texaco being one of them. If they put in enough detergent to do a good job at a "stay-clean" level, you would not need to do a stronger dose from time to time at the "clean-up" level. Doing the recommendation above will get you a "clean-up" level of detergent. You will be safe doing this level in any brand of gasoline -- will not matter.