Originally Posted By: Chris142
My new to me pickup only recomends 2 oils. 15w40 and SAE30. Gonna forget about SAE30 for now.
Would a 10w30 Diesel oil give it any better mpg? Power? It is kinda gutless w/o a turbo.
5w40? Those only come in Synthetic don't they?
Recomended OCI is 2500 miles. Personally I don't see why the currant fill of Delo 15w40 can't safely go 6-8k.
Make sure it's API CJ4. That ensures that the HTHS viscosity is at least 3.5 cP, which is the most critical spec for a diesel oil's protection on soot-induced wear.
If you use 5W-40, you might squeeze a little longer OCI, as it's fully synthetic. It will also give slightly more fuel economy than 15W-40 and be better for winter starts. Shell Rotella T6 5W-40 sells pretty cheap at Wal-Mart and it's an excellent oil. But then 15W-40 will also be perfectly fine with that engine. My favorite is Mobil Delvac Super 1300 15W-40. It's arguably better than Chevron Delo (better base oil and additive package). You can easily go for 5000 miles on either oil.
Rotella T5 10W-30 would be OK too. It's semisynthetic. It would slightly beat 15W-40 in fuel economy and power also slightly improve over 5W-40 in that respect as well.
Again, Mobil Delvac 1300 Super 15W-40 (HTHS = 4.3 cP) is perfectly fine. Shell Rotella T6 5W-40 (HTHS ~ 3.7 cP) may be an improvement but since it's slightly thinner, soot-induced wear may increase slightly. CJ-4 10W-30 (HTHS ~ 3.5 cP) is slightly thinner than 5W-40 and soot-induced wear may increase even slightly more. Also, 15W-40 will require less top-offs than 5W-40, which will in turn require much less top-offs than 10W-30.