I've not had a chance to figure my MPG on a calculator but have seen huge increases by just slowing down. I normally drive ~80 on the interstate. I stepped that down to 70 for the past 2 days. I know the overhead display isn't the most accurate thing in the world... but when it changes from 19. 7mpg @ 80 mph to 24. 5 mpg @ 70 mph that's says something for my stock '05 2500.