Ok, so today it wasn't raining so I washed and waxed the Prius. I used a clay bar, then waxed and top coated the car and went into town. For the first time ever I had a higher mileage reading when I got to town than when I left home. Usually it takes half way though town the get the mileage up to where it was at home. For the 45 mile round trip I was up 1.5 mpg's. I've never done that before. Same temp's, same speed, same traffic same everything except the wax. Keeping it clean does make a difference.