The subject of engine oil always incites so much emotional responses. This is because there still exists too much misunderstanding and myths about that liquid we pour into the motorcycle's oil sump.
One of the most dire myth is that all engine oils are the same, be it for the motorcycle, cars or trucks. All they do is lubricate the engine parts right?
Yes, it is true that the primary purpose of engine oil is to lubricate engine parts but they are formulated differently for cars, trucks, motorcycles, ships, aircraft and so forth so that is why we should stick to oils that are formulated specifically for each type of vehicle because these engines work under different types of load conditions.
But let us take a look at why we should not use car engine oil in motorcycle engines.
The motorcycle engine
- Almost all motorcycles (except a scooters and small number of exceptions) share their oil with the transmission and clutch.
- The same oil that lubricates the pistons as they whizz up and down thousands of times a minute, must also keep the gears in the transmission from grinding each other to pieces, besides avoiding the clutch plates from frying.
- As such, a motorcycle lubricant must be able to withstand high heat from combustion, shearing forces of the piston rings and gears in the transmission.
- At the same time, it must allow the clutch plates and friction plates to grip on another to allow for engine power transfer.
- On top of that, the oil film must be strong enough to withstand the forces associated with an engine revving to 12,000, 14,000 or even 18,000 RPM.
The car engine
- A car engine’s crankcase is separated from the clutch and transmission.
- Therefore, oil is circulated within the engine itself only.
- There are no shearing forces of the transmission’s gears (the gearbox uses a separate, thicker oil) and the clutch is dry (no oil).
- Car engines rarely redline above 8000 RPM.
- As such, oil makers do not have to formulate their oils to content with the gearbox, clutch and high RPM applications. Instead, they concoct their products with friction modifiers to “smoothen” the engine even further.
- This friction modifier is bad news for the motorcycle clutch as it will lead to slippage (the engine spins hard but only small amounts of power make it through).
- The clutch plates may also get worn smooth in extreme cases resulting in what is called burned clutch.
These are the reasons why motorcycle engine oils are different from car engine oils. Additionally, (except for scooters) motorcycle engine oils are JASO MA or JASO MA2 certified. The certification means that the oil is safe for use in motorcycles with wet clutches. Virtually none (although there may be a few) car oils has that certification.
In other words, please stick to engine oils that are specifically formulated for motorcycle engines.