Quote Originally Posted by Skyliner View Post
0W40 does flow better when cold but I've run 5w40 in my diesel vehicles down to -22 deg F without any issues. Mobil 1 0w40 has a propensity to shear quickly to a 20 weight and I personally wouldn't use it or recommend it in a high revving UTV engine unless you were riding in Alaska weather/temperatures.

Shell Rotella T6 is now a CK-4 oil and the CK-4 spec has less ZDDP anti-wear additives than the CJ-4 spec oil. If I were using the CK-4 spec oil, I would get a ZDDP oil additive to bolster it.

FYI to those who own a Ford Superduty 6.7L diesel: Most of the popular oils now spec'd to CK-4 do not meet Ford's specs for the engine....not enough protection against wear according to Ford.
I have been using t-6 in all my motorcycles and quads for years and will have to look into the new t-6 specs. I am a diesel tech and all i use in the new 6.7l fords is motorcraft super duty 10-30 oil as it is what is recommended and meets ford's spec. for that engine.