JASO Oil Specifications Japeneese motorcycle manufacturers found the limits demanded by the API TC specifications too loose. Oils meeting the API TC standard still produced excessive smoke and could not prevent exhaust blocking. Therefore the Japanese Engine Oil Standards Implementation Panel (JASO) introduced the following specifications: JASO FA Original spec established regulating lubricity, detergency, initial torque, exhaust smoke and exhaust system blocking. JASO FB Increased lubricity, detergency, exhaust smoke and exhaust system blocking requirements over FA. JASO FC Lubricity and initial torque requirements same as FB, however far higher detergency, exhaust smoke and exhaust system blocking requirements over FB. JASO FD Same as FC with far higher detergency requirement. Modern passenger car engine oils contain more and more friction modifiers. While this is the good thing for those segments (reduces wear and fuel consumption) it's bad for the motorcycle
