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...

 

[Bonz]

Objectively speaking it is safe...

As we learn oils are only graded on flow in cSt (centi stokes) and
they are not graded on thickness in inches nor weight in ounces...

1 cSt is the flow of water...

12.50 to 16.29 cSt is the flow of 40 grade...

16.30 to 21.89 cSt is the flow of 50 grade...

2000 cSt is the flow of honey...

Given the same temp different grades flow at different rates powered by gravity...
The measurable difference between a 40 and 50 grade is this much flow powered by gravity
As we can see the lower the cST number the quicker the flow... quicker flow does not risk
more wear... quicker flow equals lower operating temps... quicker flow equals more HP...

What is the total distance both of those oils flowed to show the 40 grade that distance ahead of the 50 grade? The difference in the picture looks like a lot, however let's look at the percentage difference over the total distance flowed. Can you share the total distance flowed?

 

[Japanese]

I really inclined to use synthetic based oil with most recent API rating, can I use SAE 10W-40 for my bike?

For the record ambient temperature here is around 25°C to 30°C, maybe up to 40° in traffic. Thanks in advance!

No, use 20W-50 as written in the manual.
You live in very hot climate. 20W-50 would be the optimum protection.

It doesn't matter that 10W-40 is Full Synthetic and API rated. It's not the right viscosity. You are looking at motor oil for cars. Also, API rating is for cars, not motorcycles.

20W-50 is more expensive in your area because there is higher demand for it (climate too hot) regardless that is not Full Synthetic.

I would drive with 20W-50 mineral after the rebuild and then probably switch to Semi Synthetic on the 2nd or 3rd oil change.

 

[Pete in PA]

Makes me wonder what oil the current production 125 cub calls for.
Bet it's 10w-30.
Since it holds less than 2 qts. I'd change the oil every 1k miles.

 

[alarmguy]

You don’t say what Climate you’re in.
If it was a moderate to cooler climate such as 50f to 80f all the time I guess it wouldn’t bother me going to a 40
Anything warmer no way

 

[CleanSump]

Owners manual is available for free download on the Honda website.
Manual states 1.1 liter sump, JASO MA because it has a wet clutch/shared sump. Pick a viscosity you feel good about, but it says SL and lower because newer specs have friction modifiers which may make the wet clutch slip.
Not going to argue it with anyone because that's what Honda says.

 

[Japanese]

My bike is a Supercub C100 series (Locally called Astrea Legenda) released on 2002.

For the record ambient temperature here is around 25 C to 30 C, maybe up to 40 in traffic. Thanks in advance!

You don’t say what Climate you’re in.
If it was a moderate to cooler climate such as 50f to 80f all the time I guess it wouldn’t bother me going to a 40
Anything warmer no way

The guy said that in his region the bike is called Honda Astrea Legenda instead of Honda Super Cub C100. Quick search shows that is most likely Indonesia or South Eastern Asia.

He also mentioned ambient temp. in Celsius (°C) and said that the temp. may reach 40°C when in traffic. That is 104°F.

Manual book says to use 20W-50, but absurdly it's more expensive here than 10W-40 while having lower specs.

His owner's manual calls for 20W-50 oil. He is thinking about API car oil because is Full Synthetic and cheaper than 20W-50 conventional and semi synth. But probably those API oils are not JASO MA/MA2.

 

[alarmguy]

So the OP rides in 77 to 85° weather.
I would stick with the manual and 20W50

 

[Bonz]

Honda clutches are no different than Kawasaki or Yamaha or Suzuki or anyone else's shared sump. Friction modifiers are only in pcmo oils rated 10w30 and lower. Anything above that and it's the rest of the oil that makes up the difference not any type of pixie dust friction modifier.

 

[ZeeOSix]

Friction modifiers are only in pcmo oils rated 10w30 and lower.

Nothing prevents an automotive oil above xW-30 to have friction modifiers in the oil. API doesn't even recognize oil above xW-30 as "Energy Conserving" mainly due to the viscosity, not the formulation.

 

[Bonz]

With that said, can anyone identify grades above 10w30 as having friction modifiers despite being disqualified because of the viscosity from the get-go? I don't know, from a business perspective, why a company would spend money on adding friction modifiers, the magic pixie dust, if the oil was disqualified from the beginning? No company would put them in if the oil wasn't going to get the rating, from a business perspective. I would put my bet on oils above 10w30 not having friction modifiers.

 

[ZeeOSix]

With that said, can anyone identify grades above 10w30 as having friction modifiers despite being disqualified because of the viscosity from the get-go? Why would a company waste money on friction modifiers, the magic pixie dust, if the oil was disqualified from the beginning?

Lots or motor oils above xW-30 use Moly, ZDDP and Boron which are types of anti-friction/anti-wear modifiers. They still use those types of additives to help reduce friction and wear ... why wouldn't they? The levels might be lower than an "Energy Conserving" xW-30 or lower, but still present.

 

[ZeeOSix]

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...

Thinner oil, including ones that shear down from use or have more temporary shear in use, produce less of a "wall" (ie, the oil film between parts), and makes moving parts rub and wear more. Lots of parts rub together in the boundry and mixed lubrication regimes. Viscosity is what keeps the parts separated, and the AF/AW additives help mitigate friction and wear when the viscosity fails to keep parts from rubbing together (ie, when the film thickness goes to zero).