I talked to the shop manager and my SA, who is the assistant service manager, at my dealer two different times about gas. They strongly recommended using top tier gas (http://www.toptiergas.com/
) and have said they have seen issues with BMWs run on non-branded and other non-top tier branded gas, such as fouled fuel injectors, etc. We normally use Shell V-Power in our BMWs and get great results. The shop manager also told me that minor fouling can be resolved by putting one container of Chevron Techron concentrate fuel injector cleaner with a full tank of gas.