Originally Posted by Boostin FD
Why bump over a year old thread?
Also, much of what dexx said is absolutely incorrect.
I read one of the threads that he linked which actually contained a lot of good information. However, in the thread lemans_blue_M states that the car will not always provide significant gain with 100 octane because it's out of the ECU's realm of adjusting timing to suit the conditions (temp, humidity, octane, etc..). This is not the case, the ECU will not adapt PAST it's targeted timing. A stock M3 runs 32 degree of targeted timing at full load @ maximum permissible RPM. If you put 100 octane in, it's not going to try to overshoot this. If you put 87 in, it will back down by a certain amount. It's not programmed to infinitely retard timing. Just thought I'd point this out. In a nutshell, higher octane will be beneficial in more extreme conditions such as high temperature, high altitude, etc.. But that's only because the car is wasn't achieving the stock targets before and now it is.
Anyway, this failure doesn't seem related to timing anyway, so I'm not helping this threads direction any