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Motorcycle oil: JASO MA vs MA2, viscosity grades and how to change it

Motorcycle oil lubricates the engine, the gearbox and, on most bikes, the wet clutch at the same time. The assistant explains which standards and grades to look for and how to do the oil change correctly.

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Answers are written by a language model solely from this base's documents, with numbered sources. They can be wrong and aren't legal, medical or financial advice: check the sources before any important decision.

Why car oil is ruled out

Modern car oils contain friction modifiers to save fuel. On a wet clutch, these additives make the plates slip: the clutch fails to transmit full power and wears early. The guides state it as an absolute rule: never put car oil in a motorcycle with a wet clutch, even at the same viscosity.

JASO MA certifies an oil as compatible with wet clutches and is the minimum for a motorcycle. JASO MA2 has higher friction indices and is recommended for sport bikes and slipper clutches. JASO MB is a low-friction oil meant for scooters with automatic transmissions and some dry-clutch bikes, never for a wet clutch.

Reading viscosity and base oil

In 10W-40, the first figure (W for winter) is cold fluidity and the second is thickness when hot. 10W-40 is the most common manufacturer grade; 10W-30 suits some small engines when the manual says so; 5W-40 helps for cold starts; 15W-50 is used for large air-cooled twins.

Mineral oil degrades faster and calls for short intervals (3,000 to 5,000 km). Semi-synthetic sits in between. Fully synthetic offers the best thermal stability and the longest intervals, but may make old seals leak on pre-1990 bikes. Always follow the grade in your manual rather than a supposedly "better" one.

The oil change, done right

Warm the engine for about 5 minutes, put the bike on a centre or paddock stand, remove the drain plug and let the oil drain for 5 to 10 minutes. Oil the new filter's seal, hand-tighten it plus three quarters of a turn (or to the specified torque).

Refit the drain plug with a new crush washer, typically at 20 to 30 Nm, as over-tightening damages the aluminium sump thread. Fill in stages, run the engine for 30 seconds, wait 2 minutes, then check the sight glass. Overfilling creates crankcase pressure and can damage seals.

Frequently asked questions

How often should I change my motorcycle's oil?

It depends on the model: the guides give 10,000 km or 1 year for a Yamaha MT-07, 12,000 km for a Honda CB500F and 6,000 km for a Kawasaki Z650. City riding with frequent stops justifies shortening the interval. Your owner's manual has the exact figure.

Can I mix two oil viscosities when topping up?

Topping up 10W-40 with 10W-50 in an emergency is not catastrophic, but the guides advise against doing it deliberately because mixing changes the grade and level of protection.

How often should I check the oil level between changes?

Every 1,000 km. Motorcycle engines naturally consume some oil, singles and sport bikes in particular.

Can I reuse the drain plug washer?

No. The crush washer (copper or aluminium) is a single-use part, and replacing it at every change protects you from an oil leak while riding.

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