Why motorcycle oil is different from car oil
The fundamental difference between motorcycle oil and car oil comes down to one word: the clutch. On most motorcycles, the clutch sits in the engine oil (wet clutch). The oil must therefore perform three functions simultaneously:
- Lubricate the engine (pistons, crankshaft, camshaft)
- Lubricate the gearbox (gears, forks, synchros)
- Enable clutch operation (controlled friction between plates)
Standard car oil contains friction modifiers (FM) that reduce internal friction to save fuel. These additives are catastrophic for a wet clutch: they cause the clutch plates to slip.
Absolute rule: never put car oil in a motorcycle with a wet clutch.
The JASO standard
- JASO MA: Certified compatible with wet clutches. Minimum requirement for any motorcycle with a wet clutch.
- JASO MA2: Enhanced version with higher friction indices. Recommended for sport bikes.
- JASO MB: Low-friction oil for scooters and dry clutch motorcycles. Never use on a wet clutch.
Viscosity grades
- 10W-40: The motorcycle standard. Good compromise for most motorcycles in temperate climates.
- 10W-30: For smaller engines (125-300cc).
- 5W-40: For cold weather riding.
- 15W-50: For air-cooled twins (Ducati, Harley-Davidson).
Mineral, semi-synthetic, or synthetic?
- Mineral: Cheapest, suitable for older engines. Change every 3,000-5,000 km.
- Semi-synthetic: Good compromise for mid-displacement motorcycles.
- Fully synthetic: Best performance. Longer intervals (6,000-12,000 km). Recommended for sport and high-performance bikes.
Practical oil change tips
- Drain when engine is warm.
- Replace the drain plug gasket at every change.
- Check drain plug torque (typically 20-30 Nm).
- Measure oil quantity and check level after running the engine.
- Record the date and mileage of the change.