Specifies ambient temperature, relative humidity, and atmospheric pressure for baseline testing.
Modern car oils often contain "friction modifiers" to improve fuel economy. However, because many motorcycles use a "wet clutch" (where the clutch is bathed in the same oil as the engine), these modifiers can cause the clutch to slip. JASO created these ratings to ensure an oil has the correct friction properties for motorcycle gearboxes and clutches. Four-Stroke Oil Ratings (4T)
Specifies ambient temperature, relative humidity, and atmospheric pressure for baseline testing.
Modern car oils often contain "friction modifiers" to improve fuel economy. However, because many motorcycles use a "wet clutch" (where the clutch is bathed in the same oil as the engine), these modifiers can cause the clutch to slip. JASO created these ratings to ensure an oil has the correct friction properties for motorcycle gearboxes and clutches. Four-Stroke Oil Ratings (4T) jaso d0144 pdf