The key for me is no ethanol. I started using Shell V power 91 because of that, since the 335i is sensitive to fuel quality. Pleased with how our cars responded with it, will continue using it and ethanol free gas for my M.
Present: 2013 M3 coupe (Azurite Black, Black, Piano Black)
Past: 2010 335i coupe (Monaco Blue, Cream Beige, Grey Poplar)
+ miata nut (2004 GT/LS and 2013 GS/Club Edition)