I know that if I run Shell I get better fuel mileage than if I run Speedway or Valero. The only one that I can give real numbers on his our Accord that I drive back and forth to work. If I run Speedway it will spit and sputter when first started and deliver about 29 MPGs, if I run Valero it will run OK and do about 30-31 MPGs. If I run Shell car runs great and I get 33 MPGs. Used to run Shell most of the time until the owner of the local Shell stations got into booz and women and forced them into bankruptcy and had to shut them down.