Ethanol

[em1toevo]

How does the 10% ethanol mixture at most fuel stations affect our engines? I have heard that it leans our car out at high rpms. Is this true? What are the long term effects?

[TouringBubble]

You will run slightly leaner at WOT ... around 3%. You'll also lose 3% MPG.

the reason behind this is that Ethanol has a stoich value of ~9.8:1 as opposed to gasoline's 14.7:1. You mix in Ethanol at a 10% ratio and the new stoich of the fuel is 14.2:1.

The ECU adds fuel during closed loop to reach the correct stoich value (technically, it aims for 1.0 lambda and not stoich) so that decreases the mileage. At WOT the ECU doesn't apply correction so no extra fuel is added and the car is slightly leaner. If you're tuned for 11.5:1 at WOT, you'll be closer to 11.85:1 with E10.

[em1toevo]

Will it hurt the engine over time?

[TripperFx3]

I have another Q. What about those guys running e85? If the stoich for e10 is 14.2 wouldn't that mean that the stoich for e85 be much lower (around 12:1?) So wouldn't they be having safe AFR's around 9.?:1?

[bomjoon]

i thought 10% ethanol gets you slightly better mileage... ??

[jktripp]

i don't know, but it tastes good!!