20W-50 to 10W-40? Is it safe?

[Bonz]

The lighter weight will unleash another 1/10th of a horsepower or so from your engine. Thanks for the post, BLS.

However a good synthetic 10W40 that does not shear down will provide similar protection vs a 20w50 conventional that may sheer down, IMO.

 

[BusyLittleShop]

The lighter weight will unleash another 1/10th of a horsepower or so from your engine. Thanks for the post, BLS.

You're welcome Bonz...

 

[TrialKid]

Here we discuss for a cub bike moped that total engine rebuilt cost not even the camshafts of GSXR 1000.

on XR650L engine that oil gets 150 Celsius temps frequently what oil for that ?

Tell me 1 oil that will not tear apart less than 1000 miles.

 

[Jetronic]

My 1979 BMW R45 airhead specs 20W50 but it runs the oil quite cool which is not surprising given it has almost the same cooling fin area as other models with double the HP. I started with 20W50 then 15w40, 10W40 and for 18 years it's run on a quality 5W40. The oil designation is not the only criteria, I consider the actually viscosity of the oil at the temperature it runs at and I'm more than happy that my 5W40 @ 85 Deg C is a similar viscosity to a 20W50 @ 100 Deg C. Bear in mind that due to lower losses, a thinner oil will run cooler than a thicker oil so the viscosity drop is not as big as you might otherwise expect. If you are going to run a thinner grade also look for as high a HTHS as available in that grade.

Ambient temperatures sound to be a good deal higher where you are so I'd measure the oil temperature after a long run before making a decision.

20W-50 was historically also chosen because it's inherently a fairly shear stable grade. Don't know if the BMW uses or has used a shared sump with the gearbox, but that would be a possible reason.

85°C, where I'd want my oil tempereature to live.....

 

[barryh]

No shared sump in BMW airheads. They are very car like in construction with separate gearbox and dry single plate clutch.

 

[Bonz]

Here we discuss for a cub bike moped that total engine rebuilt cost not even the camshafts of GSXR 1000.

on XR650L engine that oil gets 150 Celsius temps frequently what oil for that ?

Tell me 1 oil that will not tear apart less than 1000 miles.

You have asked about an extreme heat situation there may not be an answer for. Honda recommends a 2000 mile oil change interval on that bike. Based on that, they know that bike is hard on oil.

With the knowledge of XR650L oil temperatures you have shared, you must have some experience with it? Can you share what oil you have used, it would be a good start to finding the best one for the situation for those that might have that same unique and extreme use question.

 

[TrialKid]

You have asked about an extreme heat situation there may not be an answer for. Honda recommends a 2000 mile oil change interval on that bike. Based on that, they know that bike is hard on oil.

With the knowledge of XR650L oil temperatures you have shared, you must have some experience with it? Can you share what oil you have used, it would be a good start to finding the best one for the situation for those that might have that same unique and extreme use question.

Was a reference about , user worry about a small moped cub bike and search what is better.
I don't tell everyone feel his bike is unique and want to pay for the ultimate one
But that mopeds don't have any particular engine.

Now for the XR650L engine, I ride it on FMX650 bike for several thousand km.
I refer it as an example that this engine will tear apart any oil even at 20W50 in 1000km

I use on that time Torco T4SR 20W50 every 1000km

No oil cooler mod , bo Big fins cylinder head work

 

[BusyLittleShop]

Tell me 1 oil that will not tear apart less than 1000 miles.

All oils will show some degree of shear during their service but
Blackstone's used oil report data has affirmed there are no reason to
fear the shear because as our oil shears flow increases without the
dreaded increase in wear... our oil serves as a "wall" only when it is
constantly FLOWING between parts keeping them from touching...