Engine oil

Engine oil lubricates, cools and cleans the engine. On most four-stroke motorcycles the same oil also lubricates the gearbox and the wet clutch, which is why car oil is a poor choice: its friction modifiers can make the clutch slip.

Choose oil according to the owner's manual:

• Viscosity – e.g. 10W-40: the first number describes flow when cold, the second at operating temperature.
• JASO MA/MA2 – for motorcycles with a wet clutch; JASO MB – for scooters with a dry clutch.
• API class (e.g. SL, SN) – the general quality level.

A two-stroke engine needs separate 2T oil (e.g. JASO FD), mixed with the fuel or metered by an oil pump – work out the right ratio with our fuel mix calculator. Change oil and filter at the service interval and check the level regularly.