my personal experience is this-a trip to kansas driving 2000 ford crown vic. 1st tank of pure gas=25.5 mpg. 2nd tank of gas 25.3 mpg. 3rd tank 22.6 mpg. hum! did not notice the label on pump stating "contains 10% ethanol". 4th tank was 10% ethanol=21 mpg. all ... Login to read more.