93 Octane 10% Ethanol v 90 Octane 0% Ethanol

[Alex Mc]

Most every fuel pump around is running 10% Ethanol (at least here in NC) and you generally don't hear kind things about it in regards to what it can do to fuel systems not designed for it. In particular, I've heard of an inordinate amount of fuel pump replacements by a local BMW shop owner.

Just this morning I noticed that an Exxon station had a sign up for a "non-ethanol" pump, however, it is only 90 octane. I'm driving a stock B25 motor which I generally run on 93 Octane, but I'm curious if I'd be better off going to the 90 Octane and avoiding the ethanol.

Thoughts? Experiences?

[dnguyen1963]

I'll take 90 Octane 0%EtOH any day. EtOH does not pack as much energy as gasoline.

[roguetoaster]

Outside of the drop in mileage moving from a state where ethanol free fuel was easy to find to one with 10% I have noticed no appreciable degradation of fuel system components.

[jlevie]

A stock M20 & DME engine neither needs or can take advantage of anything higher than 87 octane. The only reason to run anything greater is if you have a chip tuned for higher octane.