Well I think we are saying the same thing over and over again...

I dont think I need that extra .2 seconds in the 0-60 if it costs me 7$ every fillup.

Thats just me I guess

Comparing this to a camera misses the point. With a camera, I'd want the best pics all the time. With the max, I want the best experience all the time, and I get it, all the time. Best experience doesnt come from my 0-60 score.

I almost NEVER go WOT. All I do is city cruising, or highway cruising(like most of us). I just dont need that extra power. I feel like I already have 100 hp that I dont need.

 

Ok - you make a good point.....

 

If your camera needed 4 batteries to work, then you are SOL with only 3. Now you could spend more money and buy 4 Lithium batteries (premium), or somewhat less money and buy 4 Alkaline batteries (mid-grade), or you could spend less money and buy 4 Heavy Duty batteries (regular). This is a much better analogy than yours. With all 4 sets of batteries you would be able to take pictures with your camera. But you would get more pictures (and likely not miss an important shot) with the more expensive batteries, which last longer.

Your Max only needs 87 octane to work. If you want it to work harder by frequent calls for WOT, then pay the extra for 91 octane. If you only do WOT very infrequently (like I do), why waste the money, 87 will work just fine. If you go to the track or the drag strip, by all means buy 91.

If you are asking your Max for the improved performance, by all means buy the 91 octane. If you are driving in stop-and-go traffic or just cruising at a constant 70 MPH, then regular gasoline will work just fine, and may even give you better gas mileage. Why, because octane is a resistance to premature burning of the gasoline. But this also means there is a resistance to normal burning of the gasoline.

Like all discssions of octane -- it all depends on the circumstances -- there are too many variables to state "absolute fact."

 

LoH.. u shd. write a book!


why??

(i did not read the whole thread.....sorry)

 

^^^sucks that Canada pays so much while we pay less for their product. (well for them anyway)

 

^^^ Politicians who raise taxes are what sucks. In this case it is Canadian politicians who are to blame.

 

Yes it is the politicians...both Fereral and Provincial....most of our price of gas is tax!
I just want to all lose the elections and lets start over with the Beer Party! LOL!

 

Do you guys REALLLY notice a performance difference between 87, 91, and 93? I have a 2006 SE Auto and I have only used 91 and 93 and to be honest I do not notice any difference in performance.

To also reply to the member that quoted my post earlier. You have to take into consideration where we live. I unfortunately live in one of the most expensive states and counties in the country (Westchester, NY) 93 is hitting $3.77 while 91 is anywhere from $3.43 - $3.53. Why not put 91 until the prices drop a few cents?

I won't ever use 87 because the dealer and their service center told me not to put in 87 because it will cause my car problems in the long run. Now, I'm no car expert and I can probably get away with putting 87 in my car here and there, but I honestly do not want to take the chance so I use 91 or 93.

I understand what you're saying NismoMax80, but I guess my question is. Do you really notice a difference between 91 and 93 when it comes to your car's performance?

 

i doubt there is very little difference between 91 and 93. so many sell 91 as Premium. I could never see the value in spending up to $.40 more just for 94. If I could save $.30 I might stick with 91. It's all what you decide is worth it.

Maybe I'm a sucker for ADs, but Shell's marketing that V-power cleans more makes that few cents worth it to me. I enjoyed going for the lowest bidder in my old hooptie. Now I enjoy using the highest quality to keep the max clean and ready to pass whenever needed.

I hope at least we all can agree to decide what we find as the best value and stick to it. Switching back and forth is far worse than choosing the cheapest gas. And please don't think you're doing any good or saving $$ by buying cheap gas and adding you're own additives...

 

it use to be that way before modern day ECU could adjust the timing.

 

some simple education for us all:
http://www.bajajusa.com/High%20Octane.htm

do realize if you choose lower Octane, that your maxima will change the timing. you are running your vehicle ok, but not as Nissan intended it to run. If you switch with the rise and fall of prices, you are increasing the possibility of pre-ignition and carbon buildup.


Does our compression ratio remain at 10:3? or is that what changes to run low-octane?

 

Carbon buildup will ultimately lead to a higher CR, and a higher chance for pinging.

 

This also makes that extra coin worth buying Premium to me:


http://www.daytona-sensors.com/tech_tuning.html

 

. . .

 

so i'm correct the CR is reduced? I imagine it has to in order to ignite the quicker burner/lower octane properly. But Nissan only has 10.3 listed.

I know some think "i don't WOT so 87 is fine" but I'd like to see if there are other advantages. So far I'm seeing 10.3 with 93 it the most efficient. Then at least when you switch, that tankful will be a lower MPG and possible carbon build up, if not continually.

 

I guess this is still within topic but I've read in 10 different magazines that premium pollutes less then regular, somehow it produces less carbon dioxide emissions

All car boards have gas discussions, the Prius owners are suppose to run premium

 

Close, but not quite correct. The knock-sensor will retard the timing only if it senses the engine knocking. No knocking, no retarding. The knock-sensor is designed to prevent pre-ignition, so that is not a problem. (If you experience more than a slight, occasional engine knock, you sensor has probably failed.) Also, the liklihood of carbon buildup is more dependent on the engine, the actual driving conditions, and the specific hydrocarbon content of the gasoline -- rather than on the gasoline's octane rating. And the detergents in gasoline are supposed to eliminate this buildup.
No change in compression ratio. That kind of engine would be expensive to build. However, if you have a turbo-charger mounted on the engine, it (in effect) increases the compression ration when it comes on. With a turbo, you want the highest octane you can buy.

 

well, then knowing that my engine remains at 10.3:1 I would want Premium which burns slower. More of the potential energy is used and knocking is not even a concern.

 

When my 04 was newer, I experimented with buying premium grade -- particularly on road trips. There were too many other variables to make a difinitive statement, but I got as good (and in some cases better) gas mileage with regular than I got with premium.

At the time when I posted these results here, an automotive engineer (who has not posted here in many months), SteVtec, said he thought that at steady-state driving speeds (highway cruising) the VQ engine should provide better gas mileage with regular than with premium. Who am I to argue with an automotive engineer? And my limited data tended to agree with his conclusion.

At the time I also wondered why the Honda Accord V-6 with a 10.0 to 1 compression ratio only required regular (per Honda's manual) where the Maxima at 10.3 to 1 required premium. That was when Steve pointed out that this 91 octane requirement was only for maximum performance -- frequent WOT, racing or on the dyno.

 

So - we all agree that 93 is the way to go right?
j/k

 

What about the cleaning agents added? I know Shell regular does not have those additives. I know that generally stating that "premium" gas is "better" is false, but sometimes it is true.

I don't like the idea of my ECU having to "learn" what the ignition should be...it is not perfect and will result in knocking and detonation if the fuel is not ideal for the tuning. The ECU remembers a single number, but the ECU determines timing from a table of ignition values based on throttle and manifold pressure (or flow), then adjusts based on that single number. No matter how you put it, you are losing power somewhere because you are only running ideal ignition in the last place knock was detected. In other words, the ECU detects knock, retards ignition until no more knock, then keeps that amount of retard and applies it everywhere. It might be fine to reduce it that much in that location, but you lose power when ignition is retarded in a location that doesn't need the retard. Power is power, WOT or cruising, it has a direct effect on fuel economy. Also, by not having the ideal ignition, you will have reliability issues down the road such as unburnt deposits, catalytic converter failing from unburnt fuel, premature valve wear, to name a few.

Compression doesn't have anything to do with the octane, because the ECU is controlling the timing exactly, it is nothing like a distributor setup.

 

I'm glad to see that the engine now realizes which octane it's being fed b/c it's entirely too costly to fill up with the the 93 dino juice these days!

 

This is not quite correct. The Federal Government mandates a certain treatment rate in all grades of gasoline. Common Carrier Pipeline Companies also require this minimum treatmet rate. So all gasolines have this minimum required treatmet. But most auto engineers believe that this minimum treatment is not sufficient to keep most modern engines clean. So some oil companies put a higher treatment rate in their premium gasoline. Not all do this, so your statement that "sometimes it is true" is in fact correct.
This statement is wrong. Quoting from my long post on this topic on this thread, Post # 4:
http://forums.maxima.org/showthread.php?t=296868

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

This is all from Engine Design 101. And the cylinder pressure is determined by these factors:
- Outside ambient air pressure
- Turbo-charger potentially boosting air pressure
- The engine's compression ratio (the higher the ratio, the higher the pressure just before the spark).

While computer engine control makes many improvements in engine operation, it can not completely overpower the physical factors that determine an engine's need for octane.

 

Going back to the original question...

The ECU doesn't actually detect or adapt to a change in gasoline, per se. It merely senses knock conditions (instantaneously), if they exist, and retards timing in defense. Using a lower octane fuel can increase the likelihood of knock, but does not guarantee it... cylinder pressures and temperature also factor significantly in the equation.

Regarding the "one tank" to "adapt" issue, this certainly has more to do with dilution issues in the tank than anything going on in the control system.

All arguments about power and fuel mileage come down to whether the timing is being retarded or not. Avoid conditions likely to initiate knock (and therefore retard timing) and there is no advantage to the higher octane gas. However, when conditions are conducive to knock, the timing retardation that the knocking will induce will cause reductions in both power (torque, actually) and fuel economy.

One knock inducing condition that I have not seen previously mentioned here is the low-speed/tall-gear condition likely to be encountered with an economy minded MT driver "short shifting", or most certainly in the CVT when driven "conservatively" (it loves to drop to and stay under 1500 rpm - and hold there unless you really stab the throttle). In my suburban commute I find myself in this mode more often than not, creeping along with traffic with the engine just barely above the lugging point. Across many, many, many tanks of both 87 and 91/93 octane fuel, I have consistently found under these conditions that I can go about 7-8% further on a tank of premium vs a tank of regular. Given that the cost differential for premium (in Charlotte) runs around 5%, I have no problem running the "good stuff". If I was running more "low load" highway cruising (don't do much of that 'round here), I suspect that I would see little or no difference between gasoline grades and would be more likely to use the cheaper stuff.

FYI... filled up with Shell V-Power 93 this morning... the SOBs were just changing the signs as I pulled in... but the 93 was 3.42/gal vs. 3.24/gal for 87... a 5.6% difference. Maybe others have a greater differential in their locale... I'll just consider myself lucky and take advantage while it lasts.

 

Exactly...spark advance...which is what the ECU controls and varies. Spark advance is the same thing as ignition. You are talking about the advance being constant...but it varies according to RPM, throttle and engine load. The ECU sets the advance, timing the spark exactly, but of course it is within mechanical limits determined by compression ratio and valve timing like you say, but do you know exactly what those are for a VQ to say what impact 87 octane has on those things? Don't underestimate the ECU, it can read and adjust much faster than a camshaft turns. But the ECU is not perfect and relies on the stock tune to be ideal, and it is only ideal with 91/93 octane. For the engine, the octane requirement will be a window that probably includes 87 and 93, and it is the ECU that controls all the variables, and compressoin ratio is not one of them. Compression ratio is set and does not change unless there are deposits, compression leaks, or you're building an engine in which case the ECU tune would determine the fuel used. That graph that was posted is somewhat useless, because that is not something that can be generalized when we are talking about a particular engine. Maybe it would be a good starting point if you are building an engine and want to use a particular octane, but a builder takes more into account when determining what the compression ration would be, such as experience with that particular engine. A Ford builder would have a different concept about what is ideal compared to a Mercedes builder that is starting with a better block. I have a 11.5cr stock Honda engine that definitely requires 91/93, but according to that graph I would need 100, which is race gas that in practice would give me around 20HP on top of the 220 I get on 93. Ignition would be different, as would camshaft timing, and I don't use stock ignition, mine is advanced more than stock, but the 11.5cr is stock and at least 91 octane is recommended stock. I could tune it for 87, 100, or even E85 whatever octane that is, but I tuned it for 93, so I use 93. (I hate when people say this)...Want and need are two different things...I prefer to use what the engine wants. That Taaka Vodka might fill my alcohol requirements, but 100-proof Smirnoff fills those requirements even better, also better taste with less hangover. I have no problem compensating for higher proof, just like I can also compensate for lower proof. White lightning would not fit my requirements because it has too much alcohol, the burning sensation would cause crazy belly burning and my brain would throw a CEL.

I just think that saying "if you have this compression, you must run this octane" is waaaay oversimplifying. I think the Nissan engineers are little beyond Engine 101, and they probably know a few tricks that would contradict basic assumptions and totally blow your mind...not that I know any of them...those would be company secrets not found in a textbook.

 

Lots of talk here, but the first line of the manual reads:

1-> Use 87 gasoline

So I'm thinking that if they say that, the engine is probably not struggling and retarding timing and building carbon, etc, to use that grade of fuel. It's not written :

1- use 91 gas
2- if you absolutely have to use 87, you will eventually damage the engine, but for a short period its ok...

That's not what's in the manual, but that's what you guys are saying.

Debate? Keep it simple :P

 

I'm here learning from the car GURU's. It's confusing at times reading the manual and reading what the GURU's say about the type of gas you can use in your Max. Some say you can use 87, but performance will suffer and some say 87 will kill your engine in the long run. So what is the real truth? At this point I'm now seeking an answer for my own personal education. I'm no car GURU, but I do keep my Max in great shape. I never modded my 06 Max SE the farthest I went was tint the windows...I like simplicity in my cars.

99% of the time since I purchased my car in 2006 I have used 93 octane, just recently I started to pump 91 due to the climbing gas prices. Like I mentioned earlier I have not noticed any difference in my car's performance, but then again I'm your regular driver.

EDIT:
WOOOOOOOOOT!!! I just reached the 100 post mark!!!

 

If you're not going to the track for time trials I wouldn't waste the extra money. It won't make any real difference in performance for everyday driving. The gas milage will be the same either way. Put it on the dyno w/ both flavors, it own't make much of a difference.

 

The problem is that there are many posters here who don't completely understand octane -- and don't want to learn. They "know" all they need to know -- "It's only 93 octane for my baby -- nothing but the best." Even though the manual says otherwise -- and for good reason for most drivers.

For those few who do want to learn, read all of my posts on this thread:
http://forums.maxima.org/showthread.php?t=296868
The first post tells you the different octane topics covered and which of my posts to read for that topic.

And another problem is that octane is not simple -- it is complex and there are no answers that apply to all situations. So an answer that works for one person's driving style does not work as well for another's.
If you are a "regular driver" who only very infrequently does a WOT, then you should find that regular gasoline will work fine for your driving style. If you frequently do a WOT, go to the track, want to dyno you car, or any other situation where you want the absolute best that the VQ engine can produce for you, then you should burn 91 octane gasoline (93 will work, but unless you have modded the engine, the extra 2 octane will not make any difference.)

I am a driver with 70 K miles on my 04. Except for a few tanks of premium, I have always burned the cheapest grade of gasoline in my car. Here in Colorado, that is 85 octane (see the manual for octane at altitude), in parts of the midwest (where there is a tax break) that is 89 octane midgrade, and in the rest of the country that is 87 octane regular. I have had no problems with my VQ engine, and don't expect any -- per the manual and my knowledge about octane.

Final point based on what the Nissan auto engineers tell us in the manual. "There is little doubt that if you want the absolute best performance from your VQ engine, you should burn 91 octane gasoline. But if you are satisfied with slightly less than optimum, then 89 or even 87 octane will work just fine -- and you will save some money -- not big bucks, but some.