2015 Dodge Ram 2500 — oil changes for Cummins diesels

I have a question about oil changes on Cummins diesel engines. Cummins recommends changing the oil on my 6.7L diesel every 15K miles or 12 months. I drive less than 15k per year and understood that oil does not degrade when the engine is not running. Why should I change the oil at less than 15k miles other than to help the oil companies make more money? Are diesel engines that much different than gas engines?

You’re questioning Cummins diesel engine manufacturing?


It’s your property. Do whatever you like!



Another one wanting to save a few $$$ now to spend more $$$$$ down the road.


Oil does degrade when the vehicle sits. It absorbs moisture. That is why the maintenace schedule very clearly states… Or 12 months…

If you think you know better than the folks who designed it, do what you want.

Diesel engines are VERY expensive to replace, FWIW.


It does

Because not everything is a conspiracy. Oil degrades over time and distance.

Diesel engines are generally harder on oil than gasoline engines. This is one of the reasons their oil capacities tend to be higher. Almost all modern diesels have high (vs what you see with gasoline engines) pressure turbos, and high compression ratios, and run on a fuel that tends to produce more particulates, all these things are hard on oil. Is this your first diesel?


You’ve been given very sound advice. Why are we even having a discussion over spending $50 or $60 per year?


If the maker of a gas engine says “or 12 months” it also means the safe bet is to change by 12 months, even if the mileage is low.

That said, there are owners of “garage queens” that get driven infrequently and get oil changes over longer time intervals.
Making sure each drive is long enough to fully warm up the engine and oil, and backing that up with oil analysis reduce risk.
But I recommend not to do that experiment while under warranty.

p.s., I suspect it costs more than $60 to do an oil change in that Cummins.

If you are driving less than 15000 mikes a year it usually means shorter trips, more cold starts and the engine running more time when not fully warmed up. This means more warer from condensation and more fuel washing down cold cylinder walls, thus the 12 month recommendation to get rid of the contaminants.


A diesel truck used for RV purpose may not see any short trips. If I only used this truck for 2 or 3 camping trips a year I might change the oil every other year as I do with my own truck.

As far as the cost of an oil change, we charge $85 for an oil change on a four cylinder car. This truck holds 12 quarts of oil and has a $20 filter.

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I was thinking the same thing, actually.
However, I would still change the oil once every 12 months.

[quote=“Nevada_545, post:9, topic:165414”]
A diesel truck used for RV purpose may not see any short trips.

The OP did not say it was a truck it could be a motor home and if it has a generator would add hour’s into the mix mile’s type of mile’s + hour’s to consider for when to change.

Am I the only person who thinks that an oil change interval of 15,000 miles is way too optimistic, and only intended to get the engine through the warranty period? I can remember when oil change intervals ranged from 3,000 to 5,000 miles, though maybe you can go 10,000 miles on synthetic oil, although I wouldn’t go that far. I certainly would change the oil and filter at least once a year, and of course check and top off as needed.

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how Often do you drive? Dailey? Once/week? Every 3months? Is it a camper rig? 8k over the summer and sits for 6 months?

Big difference - the Cummins takes 12 quarts of oil. Twice the oil gets you a longer change interval.

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No you aren’t the only one. On my little used Olds I would change oil once a year. The one year I had 7 miles on it and it took 8 quarts plus a filter. I don’t remember how often I changed oil in my Olds diesel during it’s 480,000 mile life but prolly somewhere around 3000 and that engine was dirtier than any of my gas engines. I always ask myself what I paid for the machine and how the cost of oil compares.

DUH. Change the oil. Are diesel engines that much different. Yes, they are. Higher compression and more blow by. Oil doesn’t just absorb water over time but combustion byproducts. As someone else said, it’s your property so do what you want, but if you are not willing to maintain it, why own it?

I change the oil in my 2012 Ram 3500 Cummins when the notification on the dash pops up. It’s factoring in time and load both, so it knows better than I do when it needs to be changed. I don’t second guess it.