Start with clutch and transmission design
Many geared motorcycles share oil between the engine, gearbox and wet clutch, so clutch friction matters. Some scooters use a different transmission design and may specify MB. Always follow the owner's manual.
Understanding the four markings
- MA: meets the MA friction-characteristic range
- MA1: one friction range within the MA family
- MA2: a higher friction range within the MA family
- MB: a lower-friction category, used by some scooters
Matching viscosity alone is not enough
A car engine oil marked 10W-40 does not automatically meet the JASO category needed by a motorcycle's wet clutch. Check SAE viscosity and JASO together.
Keep in mind
MA2 is not necessarily better for every motorcycle. Prioritise the category specified by the manufacturer.
Reference:JASO T 903:2023