i just boought a 95 maxima what octaine fuel should i use and what kind of fuel milage should i expect.

 

Manual says to use 91 octane or better. And milage depends on your driving habits. I average about 250-300 miles on one tank. And I always use Premium.

 

How much does the ECM advance the timing to take advantage of premium fuel?

I mean, because there may be no advantage running 91 to 93 seeing as higher octane fuel actually burns slower than lower octane. The way it works is the computer senses knock from the knock sensor and retards the timing if you're running a lower octane fuel that is prone to detonation (and burns quicker). In the Maxima's case due to compression ratio you should stick to 91 and above because it can compensate only so much without the thing turning into a dog. But how much does the computer ADVANCE the timing when you put 93 in? The point is to take advantage of the slower burn rate of higher octane fuel and start the combustion process earlier. Some car makers actually recommend against running higher than 91 because the car can't advance the timing enough and performance suffers. Actually the car makes less horsepower with 93 vs. 91.

Back in my hot rodding days it was all about ignition advance and racing gas. I don't think it makes a whole lot of difference now.

I can tell you I don't feel a lick of difference in my Max from 91 to 93.