Will soon own a 2014 3500 and plan to switch to synthetic motor oil at 4 or 5,000 miles. I'm wondering if the new trucks come with synthetic fluids in the diffs, transmission and transfer case. I guess I'll find out soon enough, but curiosity has gotten the best of me.

 

In the past they have come with synthetic in the trans, transfer case (ATF+4) and the differentials. Just change them per the maintenance schedule. Especially the fist time, they get nasty.

 

I know the diffs use 75-90w with GL-5. I believe the GL-5 is a friction modifier. I just changed out the rear diff cover to a mag-hytec and unused the royal purple fluid. Did the same with my F150.


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If you are buying a pick up it will come with synthetic oil.

 

The truck will come with synthetic lubes in everything but the engine. Engine comes with 15w-40 dino oil.

 

Talked with a guy at our local Cummins joint, been doing it for many moons. Asked him about synthetic in my 2013 and he recommended that I wait until I hit about 10-15,000 miles that way the engine is good and broke in, seals etc. Told me if I did it early I might have seal issues or other problems.

 

Old school way of thinking IMO. Engines are built under tighter tolerances than a long time ago when it was typical and recommended to go a few thousand miles to break it in. I would go until the first oil change and switch. No better way to break in a Cummins then having it under a load the first 10-15K. The type of oil will not change anything or hinder it's ability. I would definitely switch.

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Being the OP is in Canada he should send for the Canadian version paper copy of the owners manual. In my paper version it states that if full synthetic 5W40 oil is not used below -18C engine damage will occur, I don't recall seeing that on the DVD.