Motorcycle engines produce a lot of power for their weight. Part of the secret lies in high engine speeds.
truck engine produces peak power at about 2,500 rpm and a car engine at
about 6,000 rpm, but modern 4 stroke motorcycle engines develop peak
power at up to 15,000 rpm or more. So the circulating oil comes under
huge thermal stress as it transfers heat away from low mass components
under high power conditions.
Compact multi-cylinder, multi-valve
engines use complex oil circuitry with narrow oil ways. The oil needs to
keep flowing hot or cold. High piston speeds and power out-put generate
very high temperatures with not many places for that heat to go. So the
oil plays a crucial cooling role, which demands oils with high thermal
Deposits can build up on the pistons and rings. After a
while these can cause increased wear and reduced compression. When the
engine is working hard oil temperatures rise rapidly.
quality oil can vaporise leading to a rapid rise in oil consumption and a
fall in protection. And all the while the oil is carrying combustion by
products and wear metals into the sump and filter. Over time this leads
to the oil becoming increasingly contaminated and less effective.
demand for extended service intervals means that the oil has to remain
effective in the engine much longer, for up to a year between changes.
That's critical because motorcycle engines contain less oil than trucks
or cars and work it much harder.
Car engines have 3 separate
zones -- the engine, the clutch and the gearbox. The clutch is dry,
while the engine and gearbox use their own specific oils. But most 4
stroke motorcycle engines use a wet clutch and the lubrication system is
combined so that all these zones -- engine, gearbox and clutch rely on
the same oil.
One oil to do 3 different but equally important jobs.