Now b4 u start to flame, read the whole post.
I was test-driving an 02 Max at a dealership last week. I was talking about the poor fuel economy I get in my SUV. Here's how the conversation went:

Me: "Well, the Max isn't much better, since you have to use Premium."

Salesperson: "Well, the manual recommends that, but you don't have to use Premium."

Me: *silence* "So what do you guys put in when it's still at the dealership?"

SP: "Oh, it just depends on who's pumping the gas."

Me: "You are a f*cking idiot." (This is what I should've said that)

So what will that do to the Max? Let's say a 2002 model that's been on the dealer's lot for several months, and already has, say 200-300 miles on it? Will that cause irreversible damage? I never thought about that problem before, b/c who knows what they put in it b4 you bought it?

 

What irreversible damage? The manual itself states that you *may* use regular unleaded if there's nothing else available. It's not recommended that you use it all the time but for emergency it's okay. The engine will adjust to the lower octane.

200-300 miles is pretty much just one tank. I got my car with 31 on the odo and roughly 1/4 tank of gas... i don't know what it was but i'm guessing it was Chevron from the beginning since i also got a voucher for a full tank of Chevron gas when i drove off the lot.

 

*Oh* Well I haven't actually read the manual, since I don't have one yet. From what I had heard, I thought it said you needed to use Premium. But thanks for straightening that out for me.

 

Yep, premium is recommended but regular is okay if nothing else is available.

I forgot you don't have the manual - yet

 

Gas is gas. It's just that with a higher octane, the engine can perform better. The computer will self-adjust to whatever you put in.

 

A few hundred miles won't do damage, just cause $hitty performance. Long term use of regular may show deposits in your engine.

 

Interesting, I never tought about what kind of gas the dealer had been feeding my baby..... I use Super Unleaded!

 

if you put in low octane and really romp on the throttle (ignoring the pinging), tear up a mountain, or tow... then you can damage your engine with a quickness. Ever wonder where those parts departments get their piston ashtrays?

300 miles of test drives? Shouldnt cause any damage.

ALL of us started with regular octane from the first dealer fillup. Thats unavoidable.

If your grandmother is driving the car, then the ECU will probably be able to keep the time retarded enough to keep things safe. I wouldnt drive in a spirited fashion on regular. Youre asking for trouble. 99% chance you wont have any... but there is a chance.

My car just runs like crap on anything but Prem 93, so thats my deciding factor.

Keep in mind, altitude also dictates your fuel requirements as well.

 

I will once in a while stick in regular. I notice a slight loss in performance. But nothing major.

Dixit

 

That's the only way to go!!

 

How so?

 

i don't know the exact scientific reasoning behind it, but i believe it's like messing with your compression ratio.

and since the Max has a 10.5:1 CR, i would only run premium... the lower the octane rating, the greater the chance of ping. Ping = bad. Causes long term effects, but won't destory an engine.

 

Does Nissan put High Octane in at the factory???

 

The air is less dense at high altitude, reducing the oxygen content of each cylinder's intake cycle "charge". It is effectively equivalent to a reduction in compression ratio.

Also, actual octane requirement can vary quite a bit from engine to engine due to manufacturing tolerances. The Maxima manual takes this into account with their fuel recommendation (my 2k1 manual does, at least.) It also says a little spark knock is OK and a "good thing" under heavy acceleration as that indicates it is getting the greatest benefit from the fuel.

But then an aftermarket supercharger or turbo mod makes anything the manual suggests worthless. It's a must to use high-octane premium, especially with higher boosts, for these mods for the opposite reason you can use lower octane at high altitude: they effectively increase the compression ratio!

BuddyWh

 

By design the engine is not damaged or hurt in any way by 87 octane, it will only run it for a few miles until sold to a customer and it's cheaper.

Now you are the bean counter... what do you do...

 

Sure you do. It's right here:

http://www.nissan-techinfo.com/

Just click on "Owner Manuals" on the left side of the screen and follow the bouncing ball . . .

 

Hey that's a pretty cool link. Thanks.

 

cool thx

 

Note quite. Lower octane gas can cause premature combustion (aka ping/knock). The Max has an anti-knock sensor that will retard the timing to prevent this but it has to detect the knock first. This means some knock will inevitably occur with lower octane gas. While a slight knock for a brief period is harmless, if you do any hard driving (climbing hills, spirited acceleration, etc) you can cause severe knock to occur (however briefly before the engine adjusts) which will cause dammage. And remember, damage from severe knock is cumulative.

As for Octane ratings in general, they only tell you how much they will withstand knocking. A higher octane fuel holds no more energy than a low octane fuel. The only benefit to using higher octane fuel is from engines designed to use it (like the Max). The engine in the Max gets it's power from a higher compression ratio which in turn requires a higher octane fuel to prevent knocking. In a lower compression engine, using a higher octane fuel gives you no benefits. It does not burn any cleaner or better.

So why do we hear stories about low octane fuels causing deposits? Well, this comes back to the anti-knock sensor. In cars so equiped the ignition must be retarded to handle the lower octane fuel. It's this retarding of the timing that causes a loss in power (not the fuel itself) and non-ideal combustion of the fuel which may leave residues.

So, the gist of it all is. Yes, you can put lower octane gas in the Max if that's all that is available. No, it won't immediately destroy the engine if you drive normally. Yes, you should try to put 91 fuel in your car whenever possible to get the best possible performance.

 

My car has almost 70k miles and I dont know what kind of gas was used before I got it 2 weeks ago but I have been using 89 which, after reading the manual, may be to low. The problem is that where I live I can only get 87,89 and 93. I think Im going to move up to 93 and just pay the extra 1.50 per fill up.

One thing that I read in the manual was that Nissan doesnt recommend fuel system cleaners. I used to religiously use Redline SI-1 fuel system cleaner on my BMW and it worked great. I was going to buy some for the MAX but after reading the manual I am having second thoughts..Any opinions out there?

 

Yes many...but I believe the concensus was that unless you purchase on the recommendation of your SM...dont do it. If you wish to err on the side of caution should problems happen.

 

If the Maxima's are designed like the LS1 Camaro's and Trans Am's the knock sensors will sense detonation and signal the computer to reduce timing advance. Your engine won't produce as much hp but no damage should occur. I have an Autotap I use on my Camaro and it shows at full throttle how much timing is being pulled out if any. As long as I run premium fuel I get full timing advance. Some guys have tried regular fuel and the computer pulls out 3-5+ degrees advance.

 

you have to have detonation to sense before the timing is retarded. So I guess the arguement is how much is safe? for me, as little a possible, I may not have the car to 200K, but I'd like the option.

 

I don't think so... why?

These old stories were creations of the oil companies themselves and derive from their marketing claims that their higher octane "$upreme" fuels have more/better fuel additives (detergents, etc.) which decrease deposits better. IIRC, the FTC came down hard on them if such claims couldn't be substantiated. Which in most cases they weren't so the oil companies don't claim it any more... but they live on in old mechanic's tales.

Furthermore: it makes no sense. If your engine knocks, it follows that the same mechanism that damages the engine also acts to remove combustion chamber deposits... it has to beat through deposits before it can start removing metal. Of course it's hardly adviseable to make your engine knock severely just to reduce deposits!

Also: mild spark knock under heavy acceleration is considered normal... actually desireable... in a Maxima. It's in the manual!

BuddyWh

 

These should answer some questions.


http://www.leeric.lsu.edu/bgbb/7/ecep/trans/b/b.htm

http://www.misterfixit.com/deton.htm

http://zhome.com/ZCMnL/PICS/detonation/detonation.html

 

I never said low octane fuel would cause deposits. If you read my post again you will see I in fact said retarding the ignition may cause deposit build up. This is a completely different point. It has nothing to do with the fuel other than the fact that the lower octane causes the engine (which is designed for higher octane fuel) to work suboptimally. And whenever an engine works out of its expected parameters you can expect decreased power, decreased mileage, and perhaps residue or emissions problems. Want supporting evidence, try here (they even use a Maxima as an example):

http://cartalk.cars.com/Columns/Arch...cember/01.html

That said, for an engine designed for lower octane fuel none of this is an issue and this is where the oil companies got in trouble. They tried to tell the consumer that low octane fuel would cause problems in normal engines. It doesn't. Technically it doesn't cause any for the Max either. What the Max does to prevent knocking may though.

Again I never said knock would cause deposits. I said retarding the engine to prevent knock may cause deposits. Also, knocking the piston around would only "clean" the walls, not the valves or their seats.

And again, if you read my post you'll see I said slight knocking was harmless.

Myrv

 

You know what I get better gas mileage with lower grade gas then what I do when I put the best stuff in.

 

I was writing to your comment "So why do we hear stories about low....". I wanted to clear up where, IMO, the stories originated.

About your assertion that retarding timing itself (with nothing else at work?) is a source or cause of deposits... well... I haven't heard or read anything else to that effect. And, sorry to say, Click and Clack's waffling, unexplained and unqualified comment doesn't help convince me otherwise.

The FTC has come down on the various oil companies for a whole rashing of claims they have made concerning their fuels, I would not doubt what you relate may also be true.

Yes, you did say "slight knocking is harmless"... and I was expanding on it. Not only is it harmless... it is normal, to be expected and even desireable. And this is from the manual... a very good authority for the Maxima.

BuddyWh

 

On the topic of dealer salesmen and gas, a salesman at the Nissan dealership I go to took in a VW TDI as a trade in and put regular in it. Boy were the mechanics ****ed off cause they had to deal with it...

Sigh...

Question: What about higher octane? Can that cause different issues or is it just with lower octanes?

Axel

 

I just got my new Max, so now I have a real Owner's Manual to consult!

 

I've read of several people who got worse gas mileage using higher octane than their Max wanted.

It varies with manufacturing tolerances.

BuddyWh

 

On the highway I use regular and see no problem! With knock retard there is not an problem?

 

I've had an 87, 95, and 02 Maxima. I've always used regular gas in all of them. I don't get any pinging, and thus no engine damage is occuring. I put 237,000km on the 87, 240,000km on the 95. I've never done anything to the engines except change the oil every 5000km. (the 87 needed a timing belt at 100,000km). I don't remember the mileage i got on the 87, but on the 95 i usually got 33 miles per gallon at 66mph, on the highways and 22 in city driving in the summer. As a car gets older, the compression ratio usually increases, and some people have to switch to a higher grade of gas. I never experienced this. I've just had the 02 for a couple of months and i'm breaking it in, so i don't have much to report so far.