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

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Have a Husqvarna FE250, 2022. - 250cc 4 stroke, single cylinder, wet clutch.

Owners manual calls for a 10w-50 with the JASO spec MA2.

Have been using 10w-40 in so many bikes before this, street triples, DRZ400, DR650, WR250F, 2 stroke gearbox oils.

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

10w-50 oils are quite expensive, and if there is little gain (not fussed about power) more wanting longer engine life and better protection.

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?
 
Have a Husqvarna FE250, 2022. - 250cc 4 stroke, single cylinder, wet clutch.

Owners manual calls for a 10w-50 with the JASO spec MA2.

Have been using 10w-40 in so many bikes before this, street triples, DRZ400, DR650, WR250F, 2 stroke gearbox oils.

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

10w-50 oils are quite expensive, and if there is little gain (not fussed about power) more wanting longer engine life and better protection.

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?
What’s your climate? Coldest and hottest temps? Can’t believe nobody bothered to ask this yet… see you are Down Under so this info will help guide what you can or should do.
 
What’s your climate? Coldest and hottest temps? Can’t believe nobody bothered to ask this yet… see you are Down Under so this info will help guide what you can or should do.

Coldest winter temps I would ride in would be 5c-8c then it would probably get to about 13c.

Average temp anywhere from 15c-25c.

Hottest temps when I would ride probably hit 30c that would be the max I would want to ride this bike in.
 
Coldest winter temps I would ride in would be 5c-8c then it would probably get to about 13c.

Average temp anywhere from 15c-25c.

Hottest temps when I would ride probably hit 30c that would be the max I would want to ride this bike in.
A 20w oil is rated for operation to -20C, so there’s no real reason to avoid this in your case, and no real need for a 10w as long as you start the engine and give it a minute or so to circulate. An Xw50 is not only recommended by the mfr but is also good for use in temps up to 50C, so as someone posted above, a 20w50 appears to fit all your needs. I would not personally go below the grade recommended by the mfr, which means keeping a 50-grade oil for engine operating temps, likely specified to maintain a certain viscosity and HTHS to protect the engine. Just my $0.02.

1678340256499.png
 
No problem with the 15W50, but the 10w40 simply does not meet the viscosity requirement of the manufacturer unless you are running the oil at a cooler temperature than the manufacturer anticipated. The standard temperature for measuring the kinematic viscosity of the 50 grade oil is 100 C. If the actual oil temp is say 125 C the viscosity drops drastically.
 
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What about the 40 vs 50 part ?
Your motorcycle is water cooled, so ambient temperature should have little affect on oil temperature.
Yes, no, maybe?
I'll go with RPM having the greatest affect on oil temperature.

Next, what is the BOV, base oil viscosity of the examples given?
10w40, 15w40, SAE 40, 15w50 and 20w50
What are the viscosity of the above at 150C? (Not HTHS as the engine has roller/ball, not plain bearings.)
What are the 100C viscosity of the above examples at drain time?

The thread starter mentioned cost as a consideration.
Chevron Delo 100 SAE 40 @ USD $3.50/L (25W40)
40C 145 (call that its base oil viscosity and ISO grade)
100C 15.0
150C >4.4 (not published, just a guess)
flash point 258C
PP -24C
P .096
Zn .105
 
I have used 10/40, 10/50 and 15/50 (all synthetic) in my yam XT single 660 and I ride all year as long as it is >3deg C & not icy.

when I used 15w50, in colder temperatures, rolling the bike in neutral out of the garage was hard work and I had to engage the clutch. Otherwise there were no other operational issue other that riding gently a little longer for the thicker oil to warm up. No effect on mpg nor gear change
If you do off roading with a lot of clutch slipping, I would definitely look for a 50. I used mobil 1 15/50 but motul 300V has a much lower cold viscocity
 
Have a Husqvarna FE250, 2022. - 250cc 4 stroke, single cylinder, wet clutch.

Owners manual calls for a 10w-50 with the JASO spec MA2.

Have been using 10w-40 in so many bikes before this, street triples, DRZ400, DR650, WR250F, 2 stroke gearbox oils.

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

10w-50 oils are quite expensive, and if there is little gain (not fussed about power) more wanting longer engine life and better protection.

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?
15w50 is close enough, just about the same
Hard to know oils in another country but here in the USA any 15/50 will be fine in a clutch. I would prefer 15/50 diesel motor oil.

I dont know about over there but here I use Mystic JT-8 15w50 semi syn in my Harley, cost is about $20 USA a gallon, I buy in 2 gallon jugs.
 
Your motorcycle is water cooled, so ambient temperature should have little affect on oil temperature.
Yes, no, maybe?
What about the fact that unlike a car, his bike's oil also is the transmission lube? How does that affect the oil temp? I don't know; just posing the question.

I still wouldn't personally run a xxW40 oil when the mfr recommends a xxW50.
 
What about the fact that unlike a car, his bike's oil also is the transmission lube? How does that affect the oil temp? I don't know; just posing the question.

I still wouldn't personally run a xxW40 oil when the mfr recommends a xxW50.
Yeah, good question. The transmission gears are straight cut, so I don't think there would be much heat added to the oil.
One thing to keep in mind, thicker oils create more heat from fluid friction and rob power and fuel economy.
Not that it matters in a dirt bike how much fuel it uses, but less power is never a good thing.
HDEO single grades usually state "suitable in transmissions where an engine oil is specified".
Usually API CF/SJ MA/MA2 with all the seal compatability certifications.
 
I did this a while back for my Yamaha XSR900. I wanted to compare the W viscosity rating cold use limit against SAE J300 to see how they lined up. Yamaha is conservative on the W rating as you can see in the attachment. I pasted the J300 info of the W ratings vs use temp against the XSR900 owner's manual viscosity chart.

The Yamaha owner's manual is 15 to 20C warmer than the minimum J300 test temps on the W rating:
10W good to 10F (-10C) ... 15C warmer.
15W good to 30F (0C) ... 20C warmer.
20W good to 50F (10C) ... 25C warmer.

1678405310218.jpeg
 
A 20w oil is rated for operation to -20C.
SAE J300 says 20W is tested at -15C for cold cranking, but shows -20C for pumpability. A 20W must pass both CCS and MRV test specs to be rated a 20W, so if it did pass, it's really only good to -15C since there is no CCS spec for 20W at -20C.
 
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