Let me preface this I am asking for advice backed up with empirical evidence. I know that a lot of people have great opinions about stuff. I am trying to understand somethings. Okay I am probably going to bite the bullet and buy a new Ram 2500 with the 6.7L Cummins. I know that it’s recommended to run 10W30 but in the winter recommend 5W40. I really don’t want to change oil in October just to change it again in April. Summer temperatures are triple digits yet winter temperatures get below 0 for a while. Is it safe to run 5W40 year around even in 100 degree weather. I know there’s someone who probably has and that’s fine but they aren’t making my truck payment. So please respond with evidence based responses. Thanks and I am not going into a debate on Rotella v Valvoline. I know Cummins recommends it while Ram recommends Rottela only because Rottela has a contract with dealerships service departments. So I think either one is fine.
Cummins 6.7L general questions
- Thread starter Fishstyx
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5w40 is good for year round, I’ve done it but I suggest you do some reading in these forums on this very question like used oil analysis’.
yes... basic answer is 5w40 year round is fine on a 6.7 Cummins. Since a once a year or every 15000 miles is now the recommended service interval, just use the 5w40.
in the past 5W40 was the preferred alternate viscosity when the preferred recommended viscosity was 15W40,
meanwhile 5W40 is still the alternate recommended viscosity now that 10W30 is the preferred recommended viscosity
so the answer is yeah, 5W40 is fine year round..
in the past 5W40 was the preferred alternate viscosity when the preferred recommended viscosity was 15W40,
meanwhile 5W40 is still the alternate recommended viscosity now that 10W30 is the preferred recommended viscosity
so the answer is yeah, 5W40 is fine year round..
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They're recommending the 5w40 below 0*F almost strictly for the 5w rating of the oil. I've read that 10w gets you down to 0*F but you need 5w to go lower.
If 5w40 is safe in the winter, it's going to be safe in the summer. It's likely to be better with the improved HT/HS while still maintaining good cold flow ability.
If 5w40 is safe in the winter, it's going to be safe in the summer. It's likely to be better with the improved HT/HS while still maintaining good cold flow ability.
Over at Cumminsforum, many guys are running the 5w40 year round with no issues. In the same note, what climate are you in where 10w30 would not work?
Its been discussed on this forum how some semi synthetic 10w30 oils have similar cold flow to 5w40.
Its been discussed on this forum how some semi synthetic 10w30 oils have similar cold flow to 5w40.
As I wrote earlier from around the end of October to the end of march it can get below zero very often. I also frequent Alberta and Montana and it gets oh -60 ish in some of those places. So I really don’t want to change my oil twice a year.
Might be reasonable to consider a PAO based 5w40 for a little extra cold flow ability with those temps. 
Well, why in the hll would i miss that information? Well, public school isnt for everyone....
A quality 5w40 should be fine all around.
I normally run semi synthetic 10w30 in my 2017, tried a 24k index with semi synthetic 5w30 but found some consumption so went back and things are fine. No issues thus far in west central Sask at 150,000km. If I can bring myself to try a 40 weight, Federated Co-op makes a group 4 based 0w40 that I run in the JD skid steer.
A quality 5w40 should be fine all around.
I normally run semi synthetic 10w30 in my 2017, tried a 24k index with semi synthetic 5w30 but found some consumption so went back and things are fine. No issues thus far in west central Sask at 150,000km. If I can bring myself to try a 40 weight, Federated Co-op makes a group 4 based 0w40 that I run in the JD skid steer.
It’s easy to miss don’t worry you gave good advice. I don’t always go to those cold regions but when I do I don’t want a cold
start problem. Plus I have a block heater for when it really gets cold. Oh I should have probably mentioned that in the original post duh 
. Now this might just make this a horse of a different color.
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They likely recommend 10w30 for corporate average fuel economy reasons. I run 5w-40 in mine year round. Cummins only cares about the 5w when cold cranking in -0 degree weather. When it starts in negative weather its still going to get up to operating temperature just as it would at 20 degrees F.
I run Rotella T4 15w40 year round. It gets below 0° F occasionally. If I anticipate starting it in those temps, I usually plug in the block heater.
Thank but I stick with what’s recommended. And not to be insulting I just want to be clear what a person does with their own equipment is there business; and that’s all well and good for them I just have to say thank you for your input but the truck I am working to own does not recommend 15W40 either by Cummins or Ram.
The new 5th gens have a newer 6.7L in them with hydraulic lifters. The old school 5.9L and original 6.7L had solid lifters and could run 15w40.
I’ve heard of guys running 15w40 in the newer 6.7L’s but the owner’s manual states 5w40 or 10w30.
Just my $0.02
yeah, on the Fifth Generation Cummins in the Ram trucks they got with the mid 20th century on engine technology, tightened up the clearances, used hydraulic valve adjusters instead of flat tappets and a CGI block and came up with the 10/30 as the recommended oil.
10-30 or 5-40.
10-30 for grocery getting or 5-40 for using it for what a 2500 Cummins is built for.
No problem.
I'm using what RAM and Cummins recommended in my 2017 HO Cummins. It rolls down the road at 36K GCVW with no issue. I'd probably go with the 5w40 (which is also recommended for my truck) year round.
I've looked at the latest models, but the selection to choose from hasn't been very good, and the '17 runs great.
Good luck with your new truck.
