We had this discussion on this topic earlier this year and absolutely the TSB made no sense to anyone and has no logic in its wording.
And apparently what little sense it does make is not actually related to the winter rating. It is solely the expected base stock composition.
Not really understanding this, can you elaborate? Thanks.
Did you read the previous thread posted?
Yep
Personally I'd run 5w-40 in it all year and sleep better at night. That's what we run in our new Ram field service trucks as well. We had a new tech start at our shop last week who came from a Ram dealer. We got into an oil discussion and he stated that all they used at that dealer was Rotella T6 5w-40. He also stated that he had replaced 9 camshafts in 2019+ Rams with 6.7's in 2022 due to the owners running 15w-40. Not sure if the hydraulic lifters just don't respond properly or stick at startup. We still run solid lifters in the commercial and industrial versions of the 6.7 and it can still run 15w-40 with no issues. So I thankfully don't have to deal with that nonsense.
So if the issue was in the northern climate is it possible or probable that they were running 15w40 beyond it’s cold start ability if we were to blame the oil.
I’d say that’s highly likely, at least the only reason I can think of where the viscosity would make a big difference. There’s plenty of farmers and fleets up here in Minnesota that’ll run the same oil in all their equipment. Or people that didn’t know about the lifter change or TSB and just run the same 15w-40 that they always have and then we get a cold snap for weeks. We have fleets of school buses or box vans running the commercial version of the 6.7 with whatever cheap 15w-40 they can find with no cam or lifter issues. Can’t remember the last time we’ve even had to replace a cam in a 6.7 to be honest. So I’m sure that really muddies the water a bit too.
Doesn't the Cummins 6.7 use a water cooled Holset turbocharger? Unless you changed it to an aftermarket twin turbo or whatever, idling for two minutes isn't going to do much of anything to cool it.
Which turbo does your engine have? My 2007 Ram was the first year of the 6.7, and it had a water cooled Holset HE351VE. I have a hard time believing they don't use water cooling on the newer ones, to protect the variable geometry hardware on the compressor.
I don’t know which holset it has, but if the 2007 6.7 had one then I’d assume mine does too. I just haven’t seen anything in the literature or the owners manual that says it’s water cooled. It just mentions that it has a Variable geometry turbocharger on it.
If someone has an older diesel, like a Cummins 5.9 or one of the Mercedes 5-cylinder diesels from the 1980s, then a couple minutes of idling prior to shutdown can be beneficial, especially if the engine was pushed hard immediately before parking. Almost all turbocharged vehicles now have water cooled turbos, so the turbo bearings and oil stay relatively cool. If you're climbing a long, steep mountain grade and pull over to a rest stop it's a good idea to let it idle for a minute to let the turbo normalize. But if you're just driving normally and park the vehicle, letting it "cool" by idling for a couple of minutes isn't really doing anything.
Same as the CQ oil before it. The dexos license numbers are for Amalie products.
