I am currently running E3 plugs in my truck. After 60k miles I needed to change plugs. Thought I would try E3. They seemed to perk up the truck and mileage did improve some. Now after about 1500 miles, mileage is still good and the new found performance is still there. Maybe that is why they call it a "tune up" Are they worth the price? probably NOT Maybe just a good plug will work.