Quote:
Originally Posted by RWS-F30
On the four cylinder the manual said you could use 89, but when you do, it may throws a code to the computer that the turbo is running lean. It doesn't hurt the engine. But you may have problems down the line. For a few cents more a gallon run 91.
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No... If the manual (and gas cap) says it, then BMW intended the car to run that way. It would only run lean if: the car said 91 and I put anything less or my car was tuned and I continued to put 89. Do you listen to the manual when it says what oil to put it? If so, why no listen to it when it says what gas to put in?
Full tank of 89 gone and it drives exactly the same as 91 octane. I think people are just experiencing the placebo effect. Every body that's been in my car hasn't noticed or commented on any difference. Even after I tell him it's on 89, they say it feels just as fast.