"87" Octane In A 1995 BMW 5-Class?

Question

How harmful to my '95 BMW Would it be to use 87 octane fuel? Any opinions would be highly appreciated.

Also, is mixing different brand gasolines, like say before going to empty and you stop at a different gas station...would that be a bad thing for the vehicle/engine?

Answer 1

I drive a same model E34 BMW with the High compression 2.5L engine. Using regular on the bmw makes the ECU r****d the timing and work correctly on the 87. I have never damaged my engine at all going from premium 76 or chevron to cheap Regular arco junk gas. As a matter of fact ive gotten better gas mileage with 87 but not as much power as the 91. The Bosch ECU is very flexible and very smart even compared to modern day car ECU's. in fact Ive been running my bmw on E85 Ethanol without any problems at all for about 4 months now. The engine runs smoother and my power goes up a very noticeable, but my gas mileage goes from 21 mpg to 14 =/  can't always have both i guess. It goes to show how flexible the ECU really is.

Answer 2

The 87 octane fuel should not damage the engine at all; its when  you achieve an octane that is far too combustible, which can hurt the car. The premium gasoline may be a little better of a choice, but there should not be any problems at all. For example, I ride a 250F yamaha dirt bike, and I can use anything from 87-110 octane. I would never recommend anything over 92 octane for a street vehicle though. I know the 87 regular gasoline sells for cheaper during these times of economic instability. The brand of gasolines also does not matter, for 87 octane gasoline, is 87 octane no matter where you go. It is not bad for the engine at all. Even if you mix octanes, it will just make the octane either higher or more diluted depending on the concentration you put in. In short, it is not bad at all. If you are still uneasy, I would recommend contacting BMW dealerships to see what their recommended octane is for the car--the higher the octane, the more performance.

Hope that helps,

Tyler