I love this topic.
There is NO POINT in putting in a higher grade of gas in a car that doesn't require it. Your car won't get MORE power, it won't get BETTER mileage, you just pay an extra premium for nothing.
The purpose for higher octane is to prevent pinging. If the car is meant for 89, and you put in 94, it'll just be more resistant to pinging, but with modern cars, like the E46's which have knock sensors, it's not really an issue. I believe the 330's do require 91, so in an engine like that, i would say go with what is required.
If it's not in the manual (which i remember being the case with a 323i i had) then stick to 89 and save yourself a few bucks everytime you fill up cause the costs are just getting crazy! It's funny seeing you guys laugh about using cheap gas, and it's the price you pay for driving a BMW. If the car doesn't require it, the joke is on those that put more than required!
Last edited by Soldo; 04-24-2008 at 11:01 PM.