Hi guys, I have been running Royal Purple 15w-40 synthetic and I just can't afford it anymore. I was able to get my hands on some Rotella-T 5w-40 synthetic. Am I still safe with the different viscosity? I do live in Connecticut with frequent winter trips to NW Maine. so my truck spends it's life running in the cold.
Thanks
Anthony

 

I believe the 6.7's require the CJ-4 spec on their oils. I am pretty sure the Rotella meets that spec. I run the 5w-40 Rotella in my 5.9 and it is MUCH easier to start in the winter.

 

Yeah, I made sure the label had the CJ-4 rating, but some people I talked to said not to stray from the 15w-40 rating. I didn't think it was that big of a deal. I just wanted to make sure.