Cummins diesel oil change interval

joshuabardwell · Dec 14, 2012

I have a Ram 2500 with a Cummins diesel. The owner's manual gives two oil change intervals, depending on usage: 5,000 miles and 15,000 miles. It says to use the 5,000 mile interval if you make many short trips without bringing the engine up to temperature, if you operate in dusty environments, if you idle a lot (something like more than ten minutes out of each hour), and if you regularly operate above a certain RPM (like red-lining the truck for racing, I suppose). So, fine, I think. Even on a fifteen minute trip to the grocery store, the truck hits operating temperature. I never idle. Don't race. Don't live in the desert. Done. I'll use the 15,000 mile interval.

But then I got confused, because the manual says that "most operators will fit into the 5,000 mile category," which makes no sense to me. Assuming the truck hits operating temp even on relatively short drives, do most drivers idle their trucks all the time, or red-line them a lot? I don't think so. Seems like I'm missing something.

newbury · Dec 14, 2012

On that 15 minute trip how long does it take to get up to full operating temperature? My 7.3 takes about 5 minutes or so. Diesels aren't the best for the short trip stuff, for that an electric golf cart is better.

I say trust but verify.

At 5,000 miles of your regular routine driving get an Used Oil Analysis. An UOA tells the truth. My 7.3 dually got a good report from Blackstone Labs at 6,000 miles (Ford recommended 5,000) with advice to extend it to 8,000 miles oil change interval. But I switched to synthetic so I'll test again at 7,000 mile probably.

jinman · Dec 14, 2012

My old Cummins diesel in my Ram 2500 has had oil changed between 7k and 10k since I owned it. When I was commuting every day, it got changed at 10k. The 'ol truck just rolled over 372k miles and has never had anything except a valve adjustment. It uses no oil and starts instantly. So, I'd suggest just splitting the difference unless you tow something big or let your engine idle for hours where miles are not recorded to reflect the engine is running. You can always have your oil tested at 10k just to see what the lab will tell you. I'd bet they will tell you it is fine. 12 quarts of oil in a low sulphur diesel engine running without load should be able to go three times as long as a car with 4 quarts. More oil equals better cooling and a much greater ability to suspend contaminants so your engine stays clean and well lubricated.

dmccarty · Dec 14, 2012

Idling has put fuel in my oil per the UOA. I used to run my tractor around 1600 RPM when doing FEL work or box blading. The report came back with a bit of fuel in the oil, not a serious amount thankfully. I bumped up the RPMS to about 1800-2000 for the same amount of work and no more problems. For a year or so I was having to drive into an area I called the valley of death because of the horrible stop and go traffic. I would run about 75 miles day with maybe 5 miles or so in the bad traffic with the rest in 55 mph speed zones and very few stops. That little bit of stop and go put fuel in the oil. Again, not a bad amount but the fuel should not have been there. Thankfully I don't have to drive into the Valley of Death anymore.

Because of my driving, synthetic oil and UOA, I have driven as much as 14K on an oil change. I worked up to that distance by doing UOA and gradually increases the time/distance on the oil.

The only way for you to truly know is to do a UOA. I have used Blackstone Labs for years and they have been very helpful.

Later,
Dan

xrjohndeere · Dec 17, 2012

Run it to 7500 and change oil filter. Dont worry about how you drive it. The only time I might change at 5000 is if you idle a lot. New diesels with dpf do not like to idle.

joshuabardwell · Dec 17, 2012

xrjohndeere said:
Run it to 7500 and change oil filter. Dont worry about how you drive it. The only time I might change at 5000 is if you idle a lot. New diesels with dpf do not like to idle.

This is a 2005 model year. I don't think it has DPF. But thanks for the other advice.

hogheadCTD · Dec 17, 2012

DPF came out in 2007.5 so your good there. I have a 07 5.9 cummins, I change the oil every 5k. I think the guys running 15k on oil are using bypasses and doing regular UOA. What oil are you running?

kensnelling · Dec 18, 2012

A 15 minute trip is still considered a short trip. Very few private or local commercial usage vehicles are used in a manner that isn't considered severe usage. I know you say you don't let your truck just sit and idle. but if you do a lot of in town driving then sitting at stop lights. slow driving in parking lots, etc can add up to more low RPM usage than a person may think. Low RPM usage can add quite a bit to the cont5amination of oils.

As others mentioned, a UOA can be an eye opener as to the condition of oil. It can indicate extension or reduction in oil change intervels.

It may seem like an unnecessary expense to change oil and filter every 5K miles. but it is cheaper than repairing a Cummins engine if ther is a failure due to lubricant contamination.

Ken

hogheadCTD · Dec 18, 2012

I started my CTD up,let it idle for 15 minutes. I drained the oil and it was not even warm to the touch. It takes alot to really get these motors up to temp. I would say it takes me 10 miles of highway driving to get mine up to temp.

The best thing you can do for a Cummins is pull a heavy load for a long haul. Just my opinion.

joshuabardwell · Dec 18, 2012

hogheadCTD said:
I started my CTD up,let it idle for 15 minutes. I drained the oil and it was not even warm to the touch. It takes alot to really get these motors up to temp. I would say it takes me 10 miles of highway driving to get mine up to temp.

Not to disagree with your conclusion, that it takes longer than expected to get motors up to temp, but I'm not sure that 15 minutes of idling is a fair comparison. With every engine I've ever owned, be it gas or diesel, if I let it idle, it takes waaaay longer to get up to temp than if I am driving it. And this is true on my gas-powered car even if I'm sitting in the driver's seat pushing the RPM's to 2000 (trying to heat up an icy windshield). Two minutes of actual driving, and the engine is nearly warmed. Ten minutes of sitting in the driveway, and the needle is barely off the peg.

Like I said: I'm not trying to say that 15 minutes of driving is enough to get fully up to temp, because it sounds like consensus here is that it isn't. Just saying that 15 minutes of idling is not comparable to 15 minutes of driving.