joe@raceprecision

Use these two charts to get the recommend 93 octane, if 93 isn't available e.g. in California.

meatzorb

Both my 330i and 545i run smoother at idle on Shell 89 mid-grade. The regional BMW rep ( Erik) confirmed that the bimmers typical will run better (smoother) on mid grade 89 as long as its a listed fuel vendor on the approved list. ( which shell is)

When I put 93 in either 330i or 545i I get a lope in the idle on start-up and with the 545i I get a rough idle that continues even after warm.

I have investigated to the point of running several tanks to allow for any ECU changes etc. Confirmed with own experience and backed by BMW Regional Rep.

It's not about price here, its about the idle for me and how the engine runs. I do get about 1.5 mpg better while burning 93.

The BMW Rep also said its the detergent in the fuel that separates the gas vendors, that the approved stations do use the correct level of detergents.

Dandle

The map on the ECU is written to take advantage of AKI 91, running lower fuel the car will retard the ignition and you will loose power and MPG, the car is designed to do this and run ok though. Any more than 91 though and the car doesnt do anything as it wont recognise any higher than 91 and advance the ignition to take advantage of it, so its a waste of money.

meatzorb

Duplicate

andy535xi

agreed, I have not noticed any difference in anything between Sunoco's Ultra 94 and Shell 91. In fact, I believe that Ultra had traces of ethonol in it. Shell runs with Ferrari and they have airmiles ... good enough for me