Royal Purple 83561 Maximum Performance Motor Oil, 1 gallon Synerlec creates a tenacious ionic bond with metal surfaces, which protects engines by providing instant wear protection upon startup Duralec Ultra provides a lower coefficient of friction to save fuel and its synthetic solvency keeps internal engine parts cleaner than detergents alone Duralec Ultra motor oil is recommended for use in both two-cycle and four-cycle diesel applications including automotive, commercial fleet and stationary industrial diesel engines