The most consequential purchase decision in maintenance
Oil threads generate more strongly held opinions than any other maintenance topic, and most of the argument is about brands. The brand matters far less than the specification — and getting the specification wrong can genuinely damage your bike.
The part almost nobody knows: JASO rating
Most motorcycles run a wet clutch — the clutch sits in the same oil as the engine and gearbox. This is the fundamental difference from a car.
Many modern car oils are friction-modified for fuel economy. Those friction modifiers are exactly what a wet clutch does not want, and using them can cause clutch slip.
Motorcycle oils carry a JASO rating for this reason:
| Rating | Meaning |
|---|---|
| JASO MA | Suitable for wet clutches |
| JASO MA2 | Higher friction specification within the MA category |
| JASO MB | Lower friction — intended for machines that do NOT have a wet clutch, typically scooters with automatic transmissions |
Check your manual for which rating your bike requires. Do not assume — scooters and motorcycles in the same range can differ.
Viscosity
The two numbers — 10W-40 and so on — describe cold and hot behaviour. Use what your manual specifies. Deviating because a forum post recommended something else, or because it worked on a different bike, is how people create problems.
If you ride in extreme cold or extreme heat, your manual may list an alternative for those conditions. That is the correct place to look.
Mineral, semi-synthetic, fully synthetic
All can be correct depending on the bike. Follow the manual. A fully synthetic oil is not automatically better for an engine specified for something else.
What actually matters most
Changing it on schedule with the correct specification matters far more than which reputable brand is on the bottle. An owner using a mid-range oil changed on time will always be better off than one using a premium oil changed late.
Discussion
Post what your manual specifies for your model — rating, viscosity, and type — along with the model and year. And if you have run something different long-term, say what and why, and what your experience has been.
Do not post oil capacities. Those are model specific and belong in the service schedule thread with a manual reference.