Motorcycle engine oils

Produced from refined crude oil, lubricating oil reduces friction when placed between two moving surfaces. This protects components from wear and corrosion, keeps the engine clean and cool and acts as a sealant between the segments/pistons and jackets to prevent power-sapping gas leaks occurring from inside the combustion chamber.

Oil thins when heated and thickens when cooled. For motor oil to lubricate effectively, its viscosity – the measure of its thickness or resistance to flow – must hold up under extreme temperature conditions. A grading system like this is used: "XXW-XX", with the first part eg. "10W" indicating the oil's viscous characteristics at cold temperature and the second part eg. "40" indicating those at operating temperature. Oils which only display a single viscosity grade 30, 40, or 50 are known as a monograde. Monograde must be replaced seasonally (winter and summer) to ensure appropriate viscosity, so the majority of engine oils are now multigrade.

The oil has multiple roles. As a lubricant, it reduces the friction and wear on the bike’s moving engine parts, such as the cylinder walls and piston rings, or the camshaft lobes and followers. On many bikes the engine oil also lubricates other critical zones: the clutch, delivering the right amount of grip to avoid slipping, maintaining power; and the gears, protecting them from wear and delivering a responsive shifting. It also functions as a coolant, absorbing and transferring the heat produced in the combustion chambers and piston under-crown area, helping prevent overheating. Additionally, it’s a sealant, preventing combustion pressure escaping between the piston ring and cylinder wall. It also acts as a detergent, preventing waste matter resulting from combustion and impurities from sticking to the engine interior, keeping it cleaner. And it inhibits rust, by neutralising acids produced by combustion gases, preventing rusting and corrosion.

Motorcycle oil can be mineral-based or synthetic. Mineral oils are generally suited to older bikes and are usually less expensive than synthetic oils, which are modified to improve their protective and lubricant properties so they can perform in more advanced engines.

You should change your oil and filter at or before the end of the oil-change intervals indicated by your motorcycle manufacturer. These are based on distance travelled or time. Regular oil changing helps to keep your engine oil in good condition and provide the best protection for all your engine components.