Diesel 15W-40 for dirt bike

Can anybody give me a legit reason to not use Diesel oil in a 4T dirt bike?


The only legit reason is to give your money to a company for more marketing.

Ive ran T4 in 5 machines with no issues..

With that being said for the money Mobil 15w50 is my new sauce.
 
The only reason I can think of is if you're willing to pay for Maxima Extra which is around $18/qt. That's the only MC specific oil I've run in my bikes that didn't perceivably degrade at all.

But yeah now that Rotella T6 15W40 is a thing, it's pretty much my go to MC oil.
 
Rotella 15-40 is all my KLR and KLX have known. Use in the Yamaha Rhino as well. No issues.

For dirt applications, I change every 20 hours of run time, which is overkill.....but it makes me feel better.
 
We just came home from our annual family/friend trip to Northern NH. I run Valv 20W50 Jaso Syn in my modded 400EX, but my wife is running the T6 15W40 in her Rancher. One day trip was 100 miles. Overall mileage was about 250 for the week and it didn't use a drop and sounded good. The T6 is Jaso rated. I'm changing the 400 over to it for the winter. It's been a great oil for us.
 
I ran Rotella 5w40 and 15w40 in my Honda CRF250R and Kawasaki Ninja zx9r, never a problem
-a buddy of mine who had a couple of quads and was like “that’s a diesel oil!” I’m like no, it’s a heavy duty engine oil that people associate with diesels. Absolutely nothing wrong with running it
 
Why not? MB trucks are using 10w40 HDEO oil in their retarders...

If its good for that....its good enough for your gearboxes....
 
I’ve been running 15-40 in my 1995 Honda 300 FourTrax since it was new and it still doesn’t use any oil. No clutch slippage and shifts like new. Has only had 2 plugs in the 25 years.
 
Why not? MB trucks are using 10w40 HDEO oil in their retarders...

If its good for that....its good enough for your gearboxes....
Are the additives still high enough in CK-4 oils for motorcycle shared sumps?
I think if you pick one that meets the minimum phosphorous requirement of JASO T903:2011, 800ppm, then you should be good for gear pitting protection.
 
OP
if you had looked in the motorcycle section
you would have seen hundreds if not a thousand posts on using SRT 15w40 and other HDEOs
as i, personally, have posted on this countless times over the last 16 years on this very forum
 
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