oil for your air cooled pitbike engine, important

[Calcutta]

brilliantly put

[kaneo]

I think you guys are all forgetting that car or mower oil will make you clutch slip like crazy in the mini bikes.

[Cactus Jack]

We haven't forgotten anything ...... I posted a link in another thread which showed that "motorcycle" specific oils proved to be over priced BS when laboratory tested and compared to car oils ....

The wikipedia link says that mowers don't get anywhere near as hot as an air cooled motorcycle engine and they're right because they're constantly cooled by fan forced air . 30 weight single grade oil won't hack higher temperatures and degrades to 20 W . 20W is the best for eliminating start up wear but you need higher than 30 to compensate for viscosity loss at higher temperatures . Horizontal engines have crap cooling compared to a vertical or water cooled engine ... especially if ridden revving at low speeds so a 20w50 oil seems the best all 'round oil for use from cold to scorching summer heat .....

I've always run my worked XR75 on Valvoline XLD 20W 50 .... it's not friction modified and certainly doesn't cause clutch slip even though XR's only have a 3 plate clutch ......

[numroe]

Multigrade means the base oil is the lighter/runnier stuff, and special additives are introduced by the oil manufacturer to maintain viscosity as heat increases. When the additives break down (due to heat, acids, etc), then all you end up with is the lighter base oil - which is not viscous enough for higher temps after startup.

Single grade oils are (I believe) intended for engines which spend large amounts of time at the same running temp (eg. always on), and/or have ridiculously long oil change intervals. Eg. many diesel engine applications. Bikes don't typically fit into either of those categories.

I'd assume the single grade oil theory for lawn mowers makes the assumptions of: 1) always using super cheap oils (or rather re-badged super cheap oils in a more expensive bottle) where the oil company additive packages are also cheap and nasty, in which case a multigrade oil does not stay "multi" for long. 2) Not changing the oil often which also breaks down the higher temp viscosity additives. In which case I think single grade would make some sense for the typical neglected mower engine.

IMHO, the answer is not to use single grade oil in our bikes. The options are to use either a DECENT multigrade oil (like more expensive bike oil or a good quality diesel oil), OR just to change your oil more often - which we must do anyway due to other issues like clutch particle contaminants and/or lack of good oil filtration.

Examples of good value diesel oils (for use in bikes - and every engine you own) are Shell Rimula-X (Rotella) and Castrol Delo.

Originally Posted by pwnage5000

i work at farmright mowers and if you want a proper long life from ure engine you shouldnt use car or big bike engine oil!, the reason is that this oil is made for liquid cooled engines and is multigrade, usin this in ur pitbike can result in your oil frothing and possible ceasure due to lack of oil or if that dusnt happen the oil will still shorten the life of your engine.