I'm averaging about 24 highway, 17 city. I've calculated this using by dividing the trip miles started at the beginning of tank refill by the gallons of fuel put in at the next fill up. HKS Drop-in and all the recalls are done. Tires are not stock but are the same size 18/45/215, even with my second set of 18/45/225s the mileage is roughly the same.