Re: Actually, no....
I tried this last year with my 97 540i. I bought a 5-gallon can of Union 76, 100 octane racing fuel and dumped it into the tank with about three gallons of 91 octane fuel. It made no performance difference, although I could swear the engine ran smoother.
I posted on bimmer.org, and it resulted in some discussion, but unfortunately the archive search is still broken.
As mentioned here, I'm told you would need to chip your car of otherwise modify the engine to take advantage of higher octane fuel.
--gary
I tried this last year with my 97 540i. I bought a 5-gallon can of Union 76, 100 octane racing fuel and dumped it into the tank with about three gallons of 91 octane fuel. It made no performance difference, although I could swear the engine ran smoother.
I posted on bimmer.org, and it resulted in some discussion, but unfortunately the archive search is still broken.
As mentioned here, I'm told you would need to chip your car of otherwise modify the engine to take advantage of higher octane fuel.
--gary