I asked at the CMEP this last June when Turbo Diesel Register held a rally there. The answer was "YES" they supply all models of the 6.7L engine with full synthetic it is easier to stock just one oil type than two different oils. Also the Valvoline representative made the same statement in the fluid tech session that was held during the rally.
Jim W.
Since this came up another time, I emailed Cummins a few days ago, and received this response October 25th :
Hello Greg,
I apologize for the delay in responding to your email. We experienced a major system outage which prevented access to all our inbound email traffic. This issue has just been resolved.
Cummins only recommendation for oil is use of a 15W-40 weight that is API certified CJ-4 Low Ash oil meeting Cummins Engineering Standard 20081. All Cummins engines come from the factory containing Valvoline Premium Blue 15W-40; however, we do not endorse any brand of oil. As long as it meets the specifications, it is acceptable for use.
Cummins neither recommends nor discourages use of synthetic oil, as the use of synthetic oil will not harm your engine. However, there are no known benefits to using synthetic oil in a Cummins engine. Synthetic oils are very good for gasoline engines, since they have no oil cooler and reject more heat to less oil than diesels. It is not likely that any oil temperature achieved in your engine would harm non-synthetic oil.
Additionally, use of synthetic oil in Cummins engines will not increase our recommended oil change intervals. The maintenance intervals must still be maintained because, unlike gasoline engines, diesel engines reject a lot of soot and ash into the oil. The consistency of the oil does not affect this, because synthetic oil does not hold ash from a diesel engine any better than regular oil. The oil will still become dirty and have to be changed at the recommended interval no matter what consistency it is. Regarding deposits, diesel engines are not as affected by deposits as gasoline engines. This is because all diesel engines, regardless of manufacturer, allow a small amount of fuel into the oil. With regular oil changes, this fuel is not harmful to the engine, and actually “washes” the engine components of deposits. Leaving the oil in for extended periods will allow the oil’s fuel contamination level to become unsafe for operation, but with regular maintenance it is a normal and safe occurrence.
Thank you for contacting Cummins. We appreciate your business!
Tina
Customer Care Representative
I'm thoroughly confused now............. :confused013: