Used Cummins Diesel Questions

Cummins is a proven reliable power plant good for 500K miles with only routine maintenance. As with anything used it is all about previous owners attention to service details.

I'd have it put on the computer and checked.. if it's not that old. A bad turbocharger will set you back 3 grand.

Since you've been doing your own maint, you will find the Cummins isn't much different. Standard oil, fuel filter and air filter changes. All are easy.
For 10K a year, I would expect to pay less (probably much less) than $100 for materials. It will depend on year, eng. and number of filters.

Our Cummins 8.3 350 horse gets an oil change every 10,000 miles, that's 24 its oil, and a NAPA's best Fleet guard filter. Prices vary so run a price check in your location.
Turbines are very reliable, and seldom fail. so remember 2% of the problems with them make 100% of the stories about them.

If you're only looking at 5-10k miles a year, just plan on an oil change and all filters (oil, fuel, air, coolant, and air dryer). If you want to keep this simple and cost-effective, just find a Speedco and you'll be out the door for all of it under $500 plus air filter and air dryer. If you want to spend more, find a Cummins or RV dealer that thinks you have blank checks to pass out. Cummins builds a solid motor, but each model has had some issues that have been mostly weeded out through TSB's and recalls. I'd at least have the serial number checked for any recalls or major work performed that's not being revealed. I'd go for having an oil sample tested.

https://www.speedco.com/en-us/the-speedco-experience/rv-services

In my book the older diesels are much better. The DPF's, EGR's and common rail systems today do not create a 500k mile motor anymore.

Thanks to all. I have been told the older diesel is usually a good reliable engine up to 500k miles. At my age, 5-7 years is about the length of operations before trading for skids on a rocking chair.

Wilbur wrote:
Thinking about buying an older motorhome (100K miles or less) with Cummins but not sure something(engine) won't be masked at purchase to be a problem after writing the check. Internet sites list a lot of things to look for, but want owner/operator feedback. Also, what is the average yearly cost of ENGINE maintenance when driving is 5-10K miles per year? I'm fairly good at working on gasoline engines but no experience with diesel. Any info will be appreciated!

depends on what it is?? ISB ISC ISL etc example ISL oil is good to 20K miles;; I change oil and filter every 3 years 0r 13K miles
Fuel filters (dual) good for 4 years at 4K per year etc
air dryer about 5 years depends on type of driving (water/temps etc)
it really depends on engine size and year and miles driven for sure
however at 100K miles Iam sure its got lots of life left assuming it was decently looked after

Just pull an oil sample of the engine oil and transmission and send it to Blackstone Labs in Fort Wayne, Indiana. They will tell you if it's good or ready to puke.

Cummins is reliable, until something fails
Then the diesel parts get expensive
Several grands for a turbo
More for an injection pump
The least expensive thing on this Cummins was the water pump $54 plus labor, it is an itty bitty thing, everything else cost out the wahzoo
Cummins is one of the best engines around, but those unexpected repairs can really dent the pocket book if they happen

For those of you that put 4-5K miles a year on your Cummins DPs, do you change oil every 2-3 years, or annually? Does it hut a Diesel to sit over a winter with 4-5K miles on it when it can go 20K between oil changes? Thx, Jeff