I've gone from about 15.5Mpg to about 17Mpg over the last 3 tanks. I asked they guy at the un-service station (Chevron) what they have been puttin in there and he said that they quit using the Ethinol for the winter. Most people see a mile or two mpg increase without it. He said that some stations use it year around, so I should check before buying if I like higher mileage.