Cummins 6.7L general questions
- Thread starter Fishstyx
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I’ve run 5w40 in mine for over ten years due the temperature swings in MI. If I trade in mine on a new one I wouldn’t change a thing, 5w40 VPBE or T6. Whichever is a better price at the time I need it.
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- Dec 30, 2022
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yes, DO NOT put 15w-40 in a 2019 model year or newer 6.7 Cummins.
Just please explain how a 40grade oil can be run at -20F temperatures but not acceptable at 115F temperatures
It is unlikely the manufacturer prohibition is related to grade.
the current version of the 6.7 had a service bulletin, saying not to use 15w40 because it causes problems with the hydraulic valve adjusters... that is the only preclusion I know of 5w40 and 15w40 otherwise should behave similarly at high temperatures
I put 5w40 T6 in all the ones I service 2019 and up
Thanks but I just want to run on multi-grade oil and not change it out for just 3 months.
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most over the counter 10w30 diesel oil is going to a synthetic blend. Theres full synthetic 10w30 diesel oil but you usually have to order it only. All 5w40 diesel oil will be synthetic.
Honestly id run 5w40 year 'round and not worry about it. and make sure its CK-4 diesel oil.
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the valve train was changed in 2019 but im not sure what else rly changed from a tolerance standpoint.
I’m running 5-40 in mine but I’m not in a climate like the Arctic. A cold day for us might get down to the high teens but only for a day or two. Had a pretty warm summer though 100-106 for weeks with no rain. But haven’t done any UOA’s so can’t really give any proof that it’s working or not.
I appreciate it. Where I live it gets nasty cold December to about Feb then it gets warmer. I just don’t want to change it for just a few weeks
I’ll be willing to bet the tolerances haven’t changed in years.
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The recommendation in the owners manual is a little odd because it rarely stays in a constant negative in the US for long. From what I’ve researched on the 6.7 Cummins they are designed to run on 40 weight oil (such as 5w-40) but due to constant pressure from those epa ****bags, Cummins probably opted for the 10w-30 to please the government as 10w-30
Can net a 1-2% increase in fuel economy due to the lower rotational resistance of the 30 weight oil.
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- Jul 22, 2022
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I'm sure the 10w30 will do fine.
The trucks I service are in central Indiana (Indianapolis) many transporters. Lots go to northern Indiana to get RVs and transport to dealers. It could be -10 one morning and they could be in Atlanta that evening and it might be 60
It’s easier to stock the 5w40 only and use it year round plus it the T6 (better) than the t5 10w30
It’s easier to stock the 5w40 only and use it year round plus it the T6 (better) than the t5 10w30
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I seriously doubt that this change was due to EPA, 2500's and 3500's are not subject to the same requirements as cars and half tons.
As mentioned, the viscosity change was due to the hydraulic lifters.
Viscosity hasn't changed
depends on what particular engine you are talking about.
Standard 6.7 rear gear train models still call for 15w40 right up to the current MY.
but the front gear train 6.7 with hydraulic lash adjusters used in the Rams pickups after 2019 calls for 10w30 engine oil.. or 5w40..
