Originally Posted by mrfred

i have a gm eth content sensor. all the e85 stations i've used pump the same blend year round (76% for one station and 82% for the others), but by virtue of dilution with pump gas, i've run 60% eth a few times. i did a few logs and observed a half point richer afr and no increase in knock. i didn't retune timing to see if the lower eth had somehow pushed me past mbt, but i can say that my e85 tune felt great on 60% eth.