so will cause problems.>

Damage to the engine or exhaust system is unlikely. Many people will claim> that damage is likely with continued use of low octane fuel, but that> probably is an urban myth. I have not seen one validated example of engine,> transmission or exhaust damage from the continuous use of low octane fuel in> a high octane fuel designed engine. I have not yet read an owners manual> that said "Continued use of low octane fuel will damage the engine", anyone> read something like that in an owners manual?>

That said, there are some things that do happen. With a low octane fuel,> then engine is likely to ping, or pre-detonate under load. The Engine> Control Unit will sense this through the ping sensor and will retard the> timing. The retarded timing will result in the engine running richer than it> was designed to do

You didn't say how many gallons of 93 you pumped in, but even if it is > 50/50 you would effectively have 90 octane. I use 89 octane in my '94 > 540i often with no problems or perfromance reduction. You will not hear > pinging on lower grade gas anyway because the engine control computer will > sense the pinging before you can hear it and retard the ignition to > eliminate it. What you would sense first, if the fuel octane is too low, > is reduced performance and lower mileage.>

Remember, the pump octane rating is a minimum for that pump. It can be > considerably higher.>

-Fred W

"Put in 6 gallons of 87 octane before I realized my mistake,> and then put in 8 gallons of 93 octane">

sure he did. 6 of 87, then 8 of 93.>

Your still right though. he is still at or above 90-91 octane, so he is ok.>

Weird. I'd have sworn he said how much 87 he pumped (6 gallons) but then > only reported filling it the rest of the way with 93. But it sure does say > 6 and 8 right there...>

So it would appear that he ended up with 90.42857143 octane in the tank.