I went through the same thing when we bought our 2010 Cummins. Owners manual calls for 5W-40 full synthetic or "engine damage may occur". OK, I call up the dealership and ask them about this. I tell them that the other Cummins we had never had this requirement (1998, 2001, 2005) and all I ever used was 15W-40 conventional. They tell me that they use 15W-40 conventional in all their Cummins and have not had any problems. So I ask if I use 15W-40 conventional and have an engine problem, will they warranty it? Crickets at first and then the music began with the dancing to follow. So I've been using the Valvoline 5W-40 full synthetic. Cheap insurance.
2010 would run 15/40 and 5w/40 if you live in an ice box….. like Nord Dakota
Honestly if your 2010 is stock the oils getting so polluted with the regen strategy that synthetic is a waste. Regen is why they have the service reminder. At a calculated interval of 2-3% oil dilution the “oil change required” message comes up. They “said” that they’d tested up to 10% dilution without any ill findings. The 08-12 6.7 (pre DEF) they recommended at oil change to have the level at the “S” in safe on the stick. That would give room for growth due to fuel dilution….. I never thought I’d see the day where it was “normal” for the oil level to rise during a service interval. 08-12 was a must to delete imho……
