Door tag on my truck says to use 50wt engine oil or "winter blend" (20w50?).
Can I use 15w40 diesel oil? I'd think it has enough shear strength, and I used to run it in a Toyota five speed.
Anybody have experience with this oil in this transmission?

 

i thought a t18 used gear oil like 80w90 but 20w50 would probly be fine is there a reason you want to use 15w40 instead of 50w

 

Because I have it in gallons here, I'd have to go out and get the other stuff.