Replys are all interesting. Everything I've ever read indicates that you should use the octane recommended for the car...period. Higher octane shouldn't improve performance as its only benefit is to control early combustion in higher compression ratio cars and it doesn't provide more power (i.e., if you want to make a bomb, only use super unleaded 'cause it packe a bigger wallop? I don't think so!) . If you're supposed to run on regular and your car is older and only running well on super, then you've probably got carbon on your heads that's heating up the cylinder too much (or it's out of tune, or someother fixable item to bring the car back into spec).
My BMW owner's manual says you should use 89 octane, but you can also try 87 and if works well, then stay with it.
Wondering if those articles that ran the tests on the different grades of gas actually measured a substantive improvement in performance or was it only something like .0000001% better?
Also the comments re: different brands of gas and which is better always amuses me. If Shell watered down their gas don't ya think we'd read about it in all the papers and magazines rather than via rumors. I love urban legends!!
P.S. - Messrs Ridge and Ashcroft, if you're reading this, the bomb comment is only illustrative. I'm really really a proud American!
<span style='color:green'>1994 325i </span>- - - 75,000 mi.
No mods - - - very happy as is!
<span style='color:green'>1995 525i </span>- - - 154,000 mi.
No squeaks or rattles... unreal!