My reflection on 87 Octane (vs. 93)

[iamroddy]

Originally Posted by Fishee

I have noticed the greatest difference in mileage is due to the presence of ethanol.
No ethanol = greater mileage.
I fill up exclusively with 91 octane 0% ethanol - Shell.

I would agree with that. I am also in Southern Ontario, where we can enjoy 'corn' free gasoline, thanks to Shell's 91.
However, under certain conditions (light to moderate throttle, low speed), I occasionally hear a slight ping with 91. Petro 94 completely eliminates it.
BMW runs these things hot...having the ability to lower the coolant temp ~10 degrees F would be nice.