I was looking at my fuel mileage trend and noticed the MPG and MPH seemed to track. I did a scatter plot and got a 79% correlation between the two, which is very solid considering the number of variables. Temperature, fuel source, with or without extra filter, etc. were all ignored. It basically says to stay at 20 MPG, I need to do 60-65 MPH for the tank. That only happens on trips and I still average just under 25 lifetime with 26K miles.