jcberb

On my most recent trips to Autozone i ran across the isle which contains the various fuel additives (octane boosters, fuel line cleaners, water remover...). The labels on most of these mention their recommended use with every tank of gas. What is the deal with these...? Do any of you guys use them or recommend their use on the Max, especially the octane booster?

msoemax

Don't mess with them...they usually are a waste of money...the only one that is really needed is Heet. Use that to remove water from your gas in the winter time. Other than that the rest is really a waste of money. Gas companies have a "recipe" for gas. Car companies design their cars around this formula. When you start to add stuff in you really are taking a chance. This is especially true of oil additives. stay away from those. Either use dino oil or go with synth. Try not to mix and match stuff. Bob the oil guy has discussed this to some extent. He has done test to back up that most of the products out there are useless because they are used the wrong way/combo. Google his site up and take a look around.

Octane boosters are not worth the money...if you plan on racing try to find a station that sells the high octane variety. It will be better than dumping in your own booster IMHO. Good luck

SkoorbMax

Basically a total waste of money. All junk and in some cases, worse than junk. Slick 50, for instance, causes engine damage.

jcberb

Thanks for the feed back. I am glad i didnt put any of that stuff into my car.

vsamoylov

what bout fuel system and fuel injector cleaners?

Stephen Max

iTrader: (59)

If you really want to boost your octane, the cheapest and most effective way is to get a gallon of toluene or xylene, add 8 ounces of ATF or MMO, and add that to your gas tank. Toluene and Xylene both have octane ratings around 112-117 (I forget exactly), and they go for about $10/gal. The final octane rating of your gas plus additive obeys the rule of mixtures. So if you add a gallon of toluene to 4 gallons of 91 octane gas, you will get:

1 x 117 = 117
4 x 91 = 364
Total = 481

481/5 gal = 96.2 octane

So a gallon of your homemade additive will raise the octane rating of 4 gallons of gas by 5.2

Obviously, the more gas you add the toluene to, the lower the final octane number will be.

Compare this to an 8 oz bottle of octane booster which raises your octane rating by an advertised two or three points. That is a mere .2 or .3 (not 2 or 3).

andy044

iTrader: (5)

anyone here heard of "Restore"
pic

just in 6cylinder

mclarengts1

what will happen if you put straigt Toluene or Xylene in your tank .. like if you were to fill up on it?

Stephen Max

iTrader: (59)

You can run an engine on it, but the stoichiometric ratio will be different so the engine will have to be tuned for it. I don't know what the heating value is compared to gasoline, but I suspect you will end up with a less powerful engine. Contrary to popular belief, fuels with higher octane ratings do not necessarily have higher specific energy values, they just burn at a slower rate, thus suppressing the tendency for detonation in high compression engines.

mclarengts1

i see .. yeah cause a lot of people think the higher the better

johnny2kgle

There are two companies that make good products in this area, Schaeffer's #131C SoyUltra and Fuel Power aka FP60. Here are the links for your research.

http://www.lubecontrol.com/

http://www.schaefferoil.com/

These products are not "mass market" like most of the stuff in your big chain parts store.

eK9aT10pSi

iTrader: (1)

anymore info on the homeamde octane booster?

NmexMAX

iTrader: (22)

What more info do you want? Stephen max couldn't have covered it any better.

Chefasaurus

iTrader: (4)

I've found I can get an extra 3-5mpg by adding 3-4 gallons of 100 octane race gas, or even E85 to 3/4 tank of 93 octane. And for everyone saying, "why would you spend so much on race gas?" Think of it this way... 93 costs $3.69/gallon in downtown Chicago. 100 octane out in the suburbs is $3.89/gallon. E85 is $2.59/gallon. I've gotta figure out how to get the car tuned so it can run on straight E85. 105 octane FTMFW!

kenshi

I thought the difference is that higher octane rated fuel ignites at a higher temperature, but once ignited the burn characteristics are basically the same. This is to deal with the temperatures created by higher compression, so the fuel doesn't ignite before the spark.

SilverMax_04

You are making a common mistake with your math -- you are mixing different octane measurements. The 91 octane premium (in your example) is the posted octane number on the pump and is determined by the formula (R+M)/2 -- which is also shown on the pump. The octane rating you quote for toluene (or xylene) is measured on the Research Octane method (the R in the formula above). So you need the (R+M)/2 rating for toluene to be able to correctly do the calculation that you show above. I too don't know the exact R rating for toluene, but believe your 115 R is quite close. For many finished gasolines, the M rating is about 10 points less than the R rating. While that probably is not true for the common premium gasoline blending component toluene -- it too is probably close enough. If that is the case then toluene would have about a 105 (R+M)/2 octane rating. This is probably close enough to do the calculation that you did incorrectly above:

1 x 105 = 105
4 x 91 = 364
Total = 469

469/5 gal = 93.8 (R+M)/2 octane

Since I don't believe that a VQ engine that has not been modded can take advantage of gasoline octane higher than about 93 (Nissan designed it for 91), this should work just fine in your non-modded engine.

Stephen Max

iTrader: (59)

You are making an incorrect assumption that I was using different octane measurements. The 91 and the 117 are based on the same rating method. I forgot to mention that, though, so thanks for pointing it out.

SilverMax_04

Guess my memory is not what it used to be -- not that in my 35 years in the industry I ever worked that much with the blending of Toluene (or Xylene) in gasolines.

For information back-up I called on some of my friends from my working days who were more into this activity. One of them provided the best source for "blending octane" information, available on this web site {with my comments in these brackets -- also note the sentence I have bolded}:

http://www.refiningonline.com/engelh...ep/TCR4_29.htm

On that site we find that:
"The octane number measured in a standardized single cylinder test engine is not an absolute number but rather a relative value based on accepted standards. . . In practice octane numbers do not blend linearly. To accommodate this, complex blending calculations employing blending octane numbers as opposed to the values for pure hydrocarbons are routinely employed. There is no universal blending program used industry wide. As an improvement over octane numbers of pure compounds, there are tabulations of blending octane numbers for both RON and MON. Summarized in Table 1, these numbers are measured by blending 20 vol.% of the specific hydrocarbon in 80 vol.% of a 60/40 iso-octane/n-heptane mixture {which 80% by definition has an RON of 60 and a likely MON in the range of 45 to 55}. Although still not exactly indicative of the actual blending octane number for a specific gasoline composition, the blending octane numbers are more representative. In general, the blending octane numbers are greater than the corresponding pure octane number."

I provide all of this as an indication of how difficult it is to get a single number that represents the results of blending different components in gasoline. That being said, here is what this site in effect says is the "blending octane" for Toluene (using the test method described above) as found in Table 1, under the class of components known as Aromatics:

RON = 124
MON = 112

These blending octanes provide a blended (R+M)/2 value of 118. Given that this is only an approximation, your estimate of 117 is probably just as good an approximation as provided by this site.

As to Xylene, you will note that this site lists three different types of Xylene: O-Xylene, M-Xylene and P-Xylene. The M and P varients have very close "blending octane" values and average a 135 (R+M)/2 octane value. Not knowing, I suspect that any Xylene bought in the form of an octane booster would be the O variety which only has an (R+M)/2 value of 111 -- which is less than the value for Toluene.

Warning, you will need to be a Chemical Engineer to understand much of the discussion on this site below Table 1. Not being one, I got "lost" fairly quickly.

Guess I never understood during my career how "nebulous" these octane values actually were, so this exercise has been educational for me.

I still strongly believe that a VQ engine that has not been modded can not take advantage of gasoline octane higher than about 93 (Nissan designed it for 91).

forumboy2k2

Why would you want to put octane boost or fuel additives in your car???
It's a Nissan, not a buick, don't forget that it comes quality built straight from the factory

SilverMax_04

Some uninformed people equate higher octane in gasoline with higher energy. That is not correct. Octane is simpley the ability of gasoline to resist predetonation (burning before the spark says it's time to burn).

There are people on this site who have modded their VQ engine and claim it needs more than the Nissan-design standard of 91 octane gasoline. For them, they want to capture the benefits of this modding by using higher than 91 octane gasoline. If they believe they get better performance, who am I to say "it's all in their heads?"

And if their modding includes a turbo-charger, they are undoubtedly correct.

DeusExMaxima

iTrader: (1)

I have noticed pinging in my car. Since race gas is $9 a gallon there has to be a better way.

jbrags

forumboy you said it right on the head this guy is the only one
thats right on this topic

1st off theres no need to bump your octane unless your driving
a 70's car with no knock sensore or computers that monitor it.
in that era yah you could gain some difference but on todays
engines that are designed for 87 no

in fact what you are doing by using higher octane then necesary
is your corboning your engine heating up your catylic converter
because your engine is tuned by computere control to run on 87
octane any more octane your knock sensore will not advance it
to compensate neither will the on board computer there fore
a factory nissan has nothing to gain by using high octane

its costing you money

Stephen Max

iTrader: (59)

I believe VQ engines are designed for 91 or 93 octane fuel, but they can run fine on 87 because the knock sensor will retard ignition timing if it senses detonation. But you lose some power when the timing is retarded.

An older engine can run better on higher octane gas if there is significant carbon buildup in the combustion chambers. Carbon can increase compression ratio, resulting in detonation, and it can also cause pre-ignition due to hot spots if combustion chamber temps get high enough.

SilverMax_04

Stephen (above) is correct in all but one point. The VQ is designed for 91 octane (the highest octane "street gasoline" that can be sold in California). Unless you have modded this engine (turbo charger, etc), 91 is all you need.

You probably do have carbon build up inside of your engine -- which will raise the octane requirement of your engine. Not only do carbon deposits increase the compression ratio (slightly), but they also tend to glow when heated, causing the gasoline to burn before the engine is ready for it to burn. I recommend a treatment with Techron or similar quality fuel system cleaner. (basic Gumout is not what you need).

For more information on gasoline octane, go to my earlier posts on that topic, found here (on this site):
http://forums.maxima.org/fluids-lubr...hat-means.html

CHEF KOCH

I don't know if I am even allowed to reply to a thead this old but, my 99 VQ30DE Maxima (in New Zealand) loves 95 octane. Super smooth and goes surpisngly hard. 91 is decent but I haven't used for years. I find 98 causes it to run to rich and it has to be in 2.8/3k revs to be happy - which is fun but rough on the $$$

SilverMax_04

You are in New Zealand (and also in many other countries where the government does not control oil companies as closely as they do in the USA) the posted octane for gasoline is based on a system call The Research Octane Method. That method of measuring octanes give a higher number than the other method of measuring octane (the Motor Octane Method). There are technical reasons for using both methods which I won't go into here because it would take some digging on my part to come up with the exact details. Here in the USA the government mandates that all octane numbers posted on the pumps at stations be an average of Research and Motor. This is spelled out on the pump by the abbreviation (R+M)/2.

All of the octane numbers posted in other countries are based on the oil companies desire to post the highest possible number (makes people think they are getting more -- or the most). So they only post Research Octane. These are the numbers that you use in your quote. In most cases the Motor Octane for a gasoline will be from 11 to 9 octanes lower than the Research Octane for the same gasoline. It is usually reasonable to use an average difference of 10 octane. This difference is called "Octane Sensitivity."

If you go back into my earlier posts on this thread you will see more discussion on this difference in measurement. Here in the US, premium gasoline has an octane (R+M)/2 number of at least 91 and sometimes it can be 92 or even 93. But most premium gasoline here is 91 octane. Using the average difference of 10 between R and M would mean that the Research Octane for this premium gasoline (your octane basis) would be 96. So your Maxima would run just fine on that gasoline.

Here, if you can find 93 Octane (R+M)/2 gasoline, you will pay quite a lot more money for that product. That would likely have a Research Octane (your octane basis) of 97 to 98.

So, when reading my posts on octane, you should add at least 5 octane to each number to get an approximation of the Research Octane you are used to thinking about in your country.

Silver

CHEF KOCH

Okay, so I understand from your perspective. But what does this mean for me in New Zealand? Is my 98 actually 98 or is it 5 octanes lower?

I recently upgraded Maxima's (for anyone interested, this model of Maxima is made only in New Zealand by our Nissan department and I have literally only seen one or two my entire driving history: http://www.stuff.co.nz/motoring/road...-good-old-days ) and it specifically says to use premium petrol. I am assuming it would be rated in our country for our countries petrol and so using NZ 95 / 98 is good enough?

Hoping you can help me clear up some of the confusion.

Also, whilst I have you, Manual says 38 PSI front wheels and 35 PSI back wheels (18-inch Dunlops) does this sound about right to you? Would you recommend a different setting?

BTW thing goes ****ing HARD. VQ35DE and CVT are definitely weird but nowhere near as bad as a lot of the reviews had me believe.

-Justin

CHEF KOCH

225/45 - 18 inch to be exact