I've got Osiris Tuner on the way right now and need to make a decision on my basic tuned setup.

Right now I have 91.5 ((RON+MON)/2) 100% gas available at an increased price, which I usually fill up with because sometimes my car can sit for weeks while I'm out of town. There's only 1 station with it around, everyone else has 93 (also (RON+MON)/2) with a 10% ethanol blend at a lower price.

I don't really want to have to tune for 2 different grades so I'm leaning towards gas only for AutoX purposes and since the gas station also has a great selection of high end beer.

Is this 91.5 Gas tune going to run me extremely lean when I fill up with E10 or is there enough play for the ECU to correct it? I'm not going to be shooting for a highly aggressive tune, but considering its my daily driver, the lean condition worries me.

 

Tune the car for the gas you intend to run most often and have one of the 4 other maps set for the other fuel. Mine is that way, the 5 maps are performance, race gas, stock, valet and security. The difference between the first 2 maps is the timing.