# Recommended 10w-50, can I use a 15w-50 or a 10w-40?

SAE J300 says 20W is tested at -15C, and must be less than 9500 cP at that temp. Don't think any 20W could be rated for down to -20C if the J300 spec is -15C.
I thought it was -15C, but several charts were all at -20C.

In OP’s case it is moot since the lowest use temp will be ~40F (3C).

I thought it was -15C, but several charts were all at -20C.
Not sure if all those charts are correct and align with SAE J300 ... would have to compare.

A 20W per SAE J300 is good to an absolute minimum of -15C based on the CCS viscosity limits. The CCS is the main spec that dictates the W rating since all the MRV max viscosities are shown as 60,000 cP at every test temperature (-15C to -40C). So if an oil can pass 60,000 cP at -40C (the 0W) then it will certainly pass the MRV at any other temperature above that. So that means the CCS is the dictating test spec that will ultimately define the W rating.

In OP’s case it is moot since the lowest use temp will be ~40F (3C).
True, and even if he went by the conservative route like in the Yamaha info, he'd be good with 15W ... that's what I'd go for. And a 20W min temp is -15C (5F) with no buffer like Yamaha shows, which is well below his minimum temp estimate.

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Not sure if all those charts are correct and align with SAE J300 ... would have to compare.

A 20W per SAE J300 is good to an absolute minimum of -15C based on the CCS viscosity limits. The CCS is typically the spec that dictates the W rating since all the MRV max viscosities are shown as 60,000 cP at every test temperature (-15C to -40C). So if an oil can pass 60,000 cP at -40C (the 0W) then it will certainly pass the MRV at any other temperature above that. So that means the CCS is the dictating test spec that will ultimately define the W rating.

True, and even if he went by the conserviative route like in the Yamaha info, he'd be good with 15W ... that's what I'd go for. And a 20W min temp is -15C (5F) with no buffer like Yamaha shows, which is well below his minimum temp estimate.
We agree

Except on that oil viscosity chart that shows 20W good down to -20C (-4F). It can't be since J300 says -15C for CCS and as I explained above.

In fact, all of those oils in that chart in post #7 are going off the MRV temp spec in J300, not the CCS temp spec ... so they are all 5C too cold.

Except on that oil viscosity chart that shows 20W good down to -20C (-4F). It can't be since J300 says -15C for CCS and as I explained above.

In fact, all of those oils in that chart in post #7 are going off the MRV temp spec in J300, not the CCS temp spec ... so they are all 5C too cold.
I was conceding your point on the temps on the chart being wrong, and 20w being good for -15C. Shame on me for 3am posts

The manual doesn't give any other options? Like others have said ... I'd go with a 15W-50 then that meets the JASO MA2 so you can retain the hot "50" side of the viscosity rating.
This is what I found most interesting.

Yamaha specs weights based on Ambient temperature. Yet KTM/Husqvarna do not and just say a 10w-50.

This is why I was considering deviating from the book because other manufacturered 250 4 strokes will allow these viscosities.

Couldn't imagine the engineering is that much different where a 40 oil will impede the motor that much.

But I think I'll switch to a 50 as fuel economy and power do not outweigh longevity.

Also my bike has a cooling fan on it so that should help keep oil temps reasonable.

This is what I found most interesting.

Yamaha specs weights based on Ambient temperature. Yet KTM/Husqvarna do not and just say a 10w-50.

This is why I was considering deviating from the book because other manufacturered 250 4 strokes will allow these viscosities.

Couldn't imagine the engineering is that much different where a 40 oil will impede the motor that much.

But I think I'll switch to a 50 as fuel economy and power do not outweigh longevity.

Also my bike has a cooling fan on it so that should help keep oil temps reasonable.

The reason Husky recommends an SAE 50 when other's aren't so specific is a fairly simple story.

Many moons ago, KTMs had a design flaw and the only solution without a redesign was a thicker oil than most bikes were using, hence the SAE 50 (loose cylinder tolerances resulting in high fuel dilution). (There was a point when they even specified an SAE 60 for a different design flaw.) Anyway, even once that original design flaw was resolved and the bikes didn't have that problem any longer, they had so much success with the SAE 50 oil that they continued to recommend it.

They like it, it works, and they've had no reason to introduce variables into their formula by giving more options than necessary. It benefits Motorex, and it has been good for KTM/Husky/etc. for many years now.

The water temperature in liquid/water cooled engine does not correspond directly to oil temperature. They are two separate readings.

The water temperature in liquid/water cooled engine does not correspond directly to oil temperature. They are two separate readings.
If his bike has a coolant to oil cooler like my XSR900 has, that will help keep the oil temperature down better compated to an air to oil cooler, or no oil cooler at all.

If Husqvarna says 10w-50, that's what I would use.

The reason Husky recommends an SAE 50 when other's aren't so specific is a fairly simple story.

Many moons ago, KTMs had a design flaw and the only solution without a redesign was a thicker oil than most bikes were using, hence the SAE 50 (loose cylinder tolerances resulting in high fuel dilution). (There was a point when they even specified an SAE 60 for a different design flaw.) Anyway, even once that original design flaw was resolved and the bikes didn't have that problem any longer, they had so much success with the SAE 50 oil that they continued to recommend it.

They like it, it works, and they've had no reason to introduce variables into their formula by giving more options than necessary. It benefits Motorex, and it has been good for KTM/Husky/etc. for many years now.
Interesting - I didn't know the history of this. Do you have anything you can share so I could read up about it ?

Here's my 2 cents. I have a 2016 Kawasaki voyager with the 1700 cc water cooled engine. The manual calls for oil that meets the Jaso ma 2, or api SL rating. It says that I can run 10w40, or 20w50 depending on the temp where it's being run. But that under most circumstance's, the 10w40 is all it requires. So that's what I have been running, Valvoline regular mineral motorcycle oil. The manual say it can be run on regular oil, or the blended type, or synthetic, Doesn't seem to matter to Kawasaki what your run. The 20 w 50 version also has the same rating as the 10w40, Jaso 2. In the heat of the summer, over 75f, the temp gauge only goes up to a little over the halfway point. In cooler temps like the '40 f degree range, it only goes up to about the 1/4 mark on the gauge. Hope this gives you some help.,,,

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Would there be any issues in using a 10w-40, or a 15w-50?

Either choice will meet and exceed your mileage expectations... but the 10w40 would perform marginally better during in climate weather...

Some oil manufactures have oils that do not have friction modifiers and are safe for wet clutches but are not JASO MA certified. Does this matter?

Oils are formulated primarily for the engine and not the clutch... so you won't
see much difference between the JASO spec and non JASO spec oils to matter...

Friction Modifiers (FM) are only a small percent of the total oil
product and help the base oil do things that it otherwise could not...
(FM) fall into several basic categories but Moly, Phosphors and
Zinc are the most often used friction modifiers... some FM can be a
friction increaser...

Quote Molakule
Remember, a Friction Modifier (FM) can be a friction reducer, a
friction increaser, or one that controls friction in a specified
manner.

Starting in 1972 I have had a love affair with Huskys...

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Either choice will meet and exceed your mileage expectations... but the 10w40 would perform marginally better during in climate weather...

Oils are formulated primarily for the engine and not the clutch... so you won't
see much difference between the JASO spec and non JASO spec oils to matter...

Friction Modifiers (FM) are only a small percent of the total oil
product and help the base oil do things that it otherwise could not...
(FM) fall into several basic categories but Moly, Phosphors and
Zinc are the most often used friction modifiers... some FM can be a
friction increaser...

Quote Molakule
Remember, a Friction Modifier (FM) can be a friction reducer, a
friction increaser, or one that controls friction in a specified
manner.

Starting in 1972 I have had a love affair with Huskys...
View attachment 144704
Kinda looks like a 1975 wr 400.

The water temperature in liquid/water cooled engine does not correspond directly to oil temperature. They are two separate readings.
Yes they are two seperate readings but if your boiling coolant I can only imagine how hot the oil must be getting. While different temps, they are related.

Interesting - I didn't know the history of this. Do you have anything you can share so I could read up about it ?
I don't know that there are any written reports of this. If there are, I haven't read them. If I recall correctly it was the original KTM LC4 that had tolerance issues that necessitated the thicker oil to prevent fuel dilution, so maybe there are reports of that out there.

My post is mainly from my own experience formulating oils for Husky and my discussions with their engineers about what they wanted and expected.

Yes they are two seperate readings but if your boiling coolant I can only imagine how hot the oil must be getting. While different temps, they are related.
I think more accurate to say engine temperature has an effect on oil temperature as it does coolant temperature.
Most would be surprised that oil gets much hotter than the engine/coolant temperature or engine temperature on an air cooled bike.

In many bikes the bottom of the pistons are sprayed with oil to help cool them. In an air cooled bike like my 14 Road King I have had my oil temperature to a high about about 273 degrees such in beach traffic. Traffic jams are rare though.
On the highway is almost everyday I ride at GPS 80 MPH it will run 245 to 257 depending on air temperature, this ironically is also when the most air is being pushed through the oil cooler as at the same time the bottom of the pistons are being sprayed with oil to cool them at high speeds and results in high oil temperatures but cooler engine temperature.

As soon as I exit the highway, oil cools down to the 230s or lower at slower speeds.

Kinda looks like a 1975 wr 400.
1976 WR250 purchased from Malcolm Smith... (It's my version of a street legal Husky)

Either choice will meet and exceed your mileage expectations... but the 10w40 would perform marginally better during in climate weather...

Oils are formulated primarily for the engine and not the clutch... so you won't
see much difference between the JASO spec and non JASO spec oils to matter...

Friction Modifiers (FM) are only a small percent of the total oil
product and help the base oil do things that it otherwise could not...
(FM) fall into several basic categories but Moly, Phosphors and
Zinc are the most often used friction modifiers... some FM can be a
friction increaser...

Quote Molakule
Remember, a Friction Modifier (FM) can be a friction reducer, a
friction increaser, or one that controls friction in a specified
manner.

Starting in 1972 I have had a love affair with Huskys...
View attachment 144704
Two stroke bikes were my favorites.

Use Mobil 1, 15W-50 with confidence. The viscosity is spot on for your bike, despite the 15 vs. 10 rating. The oil is robust, won't leave deposits due to its temperature stability, and is relatively shear resistant, unlike nearly all 10W-50's. Change frequently.