I will be trying to do some experiments with variable rating my E10 and E85 percentages when filling up my car. A recent study showed my engine in a Ford to get the best mileage at E30. I filled up this weekend and added 1.5 gallons of E85 to my E10 fuel which resulted in an E17 mix. (17% Ethanol) So far I did not see a reduction in FE during a trip to St. Louis. I am using the ScanGauge to monitor the long term fuel trims. The LTFT went from -4 running E10 to 0 running E17. This is the "base" fuel trim in the PCM, so everything is right on what the PCM thinks it should be. Here are the numbers. Trip south was into a full headwind with flags flying straight out. I drove 60-65 MPH. Pulled down a 31.5 MPG trip with 2 adults, 3 kids and a stop for lunch. Rolling hills on 4-lane most of the trip. The return trip had a tail wind. Drove 60 MPH for most of the trip and pulled in a 34.5 MPG segment with no stops. I found on the last few miles that if you could drive 50 MPH you might pull out a 40 MPG average.