So what exactly is going on inside an engine when better gas is put in. I usually run the 91 Octane or whatever the higher stuff is here in CA, from Shell or Chevron. Most normal drivers just say hey... it's good for the engine and you get better gas mileage, but we all know you cant spell MPG with Chevelle ;0) Performancely speeking here, what are the benefits?

Please spend some time and look up and read FAQ Gasoline and it should tell you..

It's about 4 LONG pages/sections so will take some time..

pdq67

Originally posted by pnutkemist:
So what exactly is going on inside an engine when better gas is put in. I usually run the 91 Octane or whatever the higher stuff is here in CA, from Shell or Chevron. Most normal drivers just say hey... it's good for the engine and you get better gas mileage, but we all know you cant spell MPG with Chevelle ;0) Performancely speeking here, what are the benefits? Phil,

Putting better gas in allows you to put your spark advance in at a point where it does the most good. Ideally, you want the location of peak pressure to occur between 10-15 degrees ATDC. If you have a cheap low octane gasoline, you may hit borderline detonation before you can advance spark enough.

Having said that, even if you did adjust the spark to take advantage of the higher octane, it would still cost you as much or more per mile to run the premium fuel.

Yes, you can spell mpg with Chevelle. There are plenty of dudes cruising around this site that regularly get 17+ mpg while enjoying 300+ h.p.

Mike

One of my biggest pet peeves is when somebody calls the higher octane gas "better". It's not better. It's not good, it's not bad. It's just different than the lower octane fuels. It doesn't contain any more energy, it wont give you better MPG, and you're not "treating your car right" by giving it 91 or 92 every once in a while. It just burns slower.

The only time 92 is better is if your engine cannot handle 89 or 87. Keep in mind that some engines make more power with 87 if they can handle it, due to the faster burn rate.