I had a Ram Cummins and drove a Cummins for a decade, and you need diesel oil. Chevron Delvac or Rotella are the two most popular,
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esters, look it up. I am sure Amsoil has a bypass filter for u, with a bypass filter you can easily go 30k on an oil change with your engine. You may want to run a UOA from blackstome half way through, but diesels do not need clean oil like gas engines do. Even if you are playing it safe, a 15k miles oil change is nothing with a diesel, all assuming you have proper filtration. Amsoil AE filters are synthetic, and will filter that oil for 30k easily. Some guys go 50k with a bypass, some go 100k and some go over that. Google it, 100k oil change interval, or 300k oil change interval. It is diesel specific, best you can get on gas is 25k. It is the most important upgrade for any diesel in my opinion, get a bypass filter. You should really join the TDR website and learn more, that is the Cummins specific website and those guys know what they are doing. Owning a Cummins is like joining a killer freak club, go be a freak over there, good stuff.
Sounds kinda soon for fuel filters, but that is also the rub with diesel. It is a dirty fuel and often will mess up filters, and really no way around that. Always get your fuel and a reputable place like Chevron. I haven't owned for a long time, but back in the day it really mattered where u get the fuel. Do you have a water separator, dunna with the 14's? I remember they had some options with filtration over on tdr, I just forget them it has been so long. The Ram forum is no slouch, killer info here too, so tap both sites for good info. But register at the Turbo Diesel Registry, TDR.
A family member owns a landscape business, all of his 6 vehicles are Cummins, and he has been on a 30k oil change interval with a bypass filter since day one. Only his heavy equipment trucks that carry the heavy tow loads get a 15k oil change interval. He has been in business for 30 years give or take, never had any issue with the engines other then fuel pumps none related. Some issues with the tranny's, because he tows heavy stuff and they eat tranny's, but those engines are damn near bullet proof.
You do have to change one of the filters sooner, like every 5k, but the other bypass filter will go the 30k no problem. I forget the actual numbers on the filters, like I said it has been over 15 years for me, but they know this stuff over on TDR.