Amsoil in the transmission, differentials and engine. My car has 209,000 miles and zero problems with any of the components lubricated with Amsoil. Would the same be true if I were using Mobil 1, Royal Purple or Dino Oil? I'll never know. I like the 15k drain interval in the Jeep and 25k interval in my car. It offsets the price of the oil for us high mileage commuters.