I will check my mileage at the next fill-up the normal way, you know, miles/gallon and see if the displayed number holds true, seems like it just keeps getting higher, when I left the dealership with 8 miles on the car, it was displaying 18 MPG, now it's up to 26 MPG, hopefully the best is yet to come. I have a 84 miles/day commute, but with the mileage I get on this and I will only have to fill up once a week on a 15-gallon tank, amazing.