PSC's SAE 30 Oil category represents lubricants that have a viscosity grade of SAE (Society of Automotive Engineers) 30. This grading system tells you the thickness of the oil and how it is affected by temperature. In this case, the "30" represents the thickness of the oil at operating temperature. The higher the number, the thicker the oil is between 2 mating surfaces. This oil is what is considered a Mono-Grade or Straight Weight oil which doesn't include a "W" performance grade.