Quote Originally Posted by Walcrow View Post
Does the BMW REQUIRE premium gas regarding pre-ignition OR does it require it to achieve the HP rating? Germans are good at putting Premium required for max HP but many will run on regular and the HP drops down. I doubt, IMO, that the BMW has to have premium to run. My old VW Vanagon with the VR6 engine stated the same, that it needed high test gas. The service tech back then told me that was for max HP and run it on mid grade or worse if necessary. It ran fine on either.
I think this is pretty much the case. I have a VW GTI which the manual says requires premium. According to the GTI Forum, it will run just fine on a lower octane except the computer makes adjustments in the timing to avoid detonation but at a small sacrifice in HP. I wouldn't know since mine has never had any gas other than Shell V-Power and all is well.