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Quote:

Originally Posted by AlexK (Post 798237)

What are you talking about - the current US manual for new X3 says "BMW recommends AKI 91 or 89", in addition to saying that "minimum AKI rating is 89" and "do not use E85 fuel", plus stuff like "Fuels containing up to and including 10 % ethanol or other oxygenates with up to 2.8 % oxygen
by weight, that is, 15 % MTBE or 3 % methanol plus an equivalent amount of co-solvent, will not void the applicable warranties with respect to
defects in materials or workmanship." That, to me, is a pretty specific information.

BMW prints that in the US manual because they know that fuels in the US vary widely in quality and tend to be poorer than those sold in the EU.

The German version of those manuals (which are the ones I go primarily by) states what I mentioned in the other post, and I believe the Australians and other non-US members can back me up.

My 2008 535i owner's manual (Canada) says minimum 87 AKI, and some other words about recommended AKI. They appear to be more relaxed about Canadian fuels. Your problem is that you get too much crap fuel in the US, so BMW has always recommended higher AKI as an insurance policy to allow for the fact that some of your 91 AKI isn't really 91 AKI despite being so labelled. They have been doing it for years, and have many owners in the US convinced that their BMW engines can only run on 91 AKI.

91 RON is pretty close to 87 AKI for many fuels.

I do agree with Fraser that the newer engines have better DME controls over knock.