Tips For Keeping Cummins Motor Oil From Becoming Gritty

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Goose55

Senior Member
Joined
Aug 29, 2020
Posts
751
Reaction score
421
Location
Ajo, AZ
Ram Year
2019
Engine
Cummins High Output 6.7L
In my last trip to Service I happened upon the Cummins authority there and his advice was really appreciated, so I thought I would share this information. I asked about why 12 quarts of oil becomes as dirty as it did at only 5,000 miles. True, diesel engine oil will turn black rather quickly but it also felt gritty and he told me that can really become an issue, especially for the push rods and rocker arms. So badly that they become noisy.

His advice was to change the oil religiously at 5,000. Also, in driving just around town as I often do, he said to use the gear limit toggle switch to down shift to keep the RPMs up. So, I now do that at 25 mph--so that the RPM is at or above 1,500, whereas before it was about 1,110. Also, in reading up again in the Owners Guide and Diesel Supplement (and because it is Winter now--though only mildly in S Arizona) my goal is not to ever shut the engine down before it has reached at or near operating temperature. So, if I have a brief stop at the Post Office or Circle K, I use the cruise control buttons to idle the engine up. After idling the engine up, I increase the RPMs further by tapping the "Resume" button so that it idles at around 1,300 or 1,400.

All this to help prevent un-burned diesel fuel from getting into the crank case.
 

HEMIMANN

Senior Member
Supporting Member
Military
Joined
Dec 7, 2020
Posts
6,795
Reaction score
17,078
Location
Minneapolis, MN
Ram Year
2017 2500 Laramie Crew Cab
Engine
6.4L HEMI
Operating temperature is key for diesel engine longevity for sure. The new engines won't wet stack like the mechanical engines did at long term low idle, but it's still not a good operating regime, and your guy is still right that cold combustion promotes oil contamination over time.

I'd only change diesel oil @ 5k OCI if I idled a lot, or ran in cold climate a lot. Otherwise, the manual OCI is fine. Not sure what they're up to these days - I'd heard 15,000 miles or some such? Retired from Cummins in 2016.
 

raggdoll

Senior Member
Joined
Aug 16, 2016
Posts
110
Reaction score
55
Location
North of Toronto
Ram Year
2016 Laramie, 2018 Sport, 2021 3500 6.7, 2014 Sport, 2021 Classic Night Express
Engine
hemi 5.7
If I had to change the oil every 5k I'd sell it...
 
OP
OP
Goose55

Goose55

Senior Member
Joined
Aug 29, 2020
Posts
751
Reaction score
421
Location
Ajo, AZ
Ram Year
2019
Engine
Cummins High Output 6.7L
I am finding it is true, that turning on full exhaust brake after starting my cold Cummins, rapidly increases coolant temperature. Also, after a few moments, I idle it up to about 1,500 rpm using the speed control buttons. A word to the wise. Just sayin'.
 

tex68w

Member
Joined
May 10, 2021
Posts
58
Reaction score
14
Location
Texas
Ram Year
2021
Engine
6.7L CTD
I have been changing my oil at 7500 mile intervals with Shell Rotella T5 synthetic blend but I might stretch it to every 10K miles on this next OCI and run T6 full synthetic. I can't let it go every 15K like the manufacturer suggests, that's just too long for my OCD lol.
 
Top