newer Cummins 6.7L ... 5w40 vs 15w40

[kschachn]

I'm not convinced this an accurate statement, but thats just me.

It’s not the 15W winter rating. Viscosity is completely dependent on temperature and if it really were the winter rating then a 15W would be fine at any temperature above about 15 degrees. This has been discussed here many times and the gist of the prohibition is a blanket assumption about 15W-40 base stocks.

It’s a rather goofy “lowest common denominator” statement rather than actually addressing the situation.

 

[kschachn]

Deposits.

FCA thinks running full syn will prevent the deposits formed when someone runs bargain basement conventional 15w-40 at their nonsense 15k OCIs.

They don't want you running conventional so they blanket banned all 15w-40. All the punters think it's because it's related to flow. It's not.

Pick a 5w-40 and stick with it. Delo, Delvac, Rotella, even Fram, etc.

This.

 

[Ruby]

It's interesting how the 2019 and newer Ram Diesel's must run either the 10w30 or 5w40, no more 15w40 oil because of lifter design. I own a 2011 3500 6.7. My Diesel Supplement gives me two choices 15w40 at temperatures Zero and above or 5w40 in all temperatures. I choose to run the Rotella T6 5w40 year round, 5000 mile oil changes with either the Fleetguard Stratapore LF16035 or the Mopar MO-285. I have never had any issues with the Rotella T6 5w40. It does real well with winter cold starts ( Anti-gel Use As Well) in freezing temperatures without plugging in and does well in the summer temperatures as well.

I guess, if I had a newer Ram with the Cummins, I would not want to take a chance using the 15w40 because of the lifter design. I'm thinking that if the truck was still under any type of warranty, there would be an oil sample analyses to make sure the proper type of oil was used due to the expensive repair costs. If the truck is out of warranty, I still would not use the 15w40, just my opinion.

 

[kschachn]

It's interesting how the 2019 and newer Ram Diesel's must run either the 10w30 or 5w40, no more 15w40 oil because of lifter design. I own a 2011 3500 6.7. My Diesel Supplement gives me two choices 15w40 at temperatures Zero and above or 5w40 in all temperatures. I choose to run the Rotella T6 5w40 year round, 5000 mile oil changes with either the Fleetguard Stratapore LF16035 or the Mopar MO-285. I have never had any issues with the Rotella T6 5w40. It does real well with winter cold starts ( Anti-gel Use As Well) in freezing temperatures without plugging in and does well in the summer temperatures as well.

I guess, if I had a newer Ram with the Cummins, I would not want to take a chance using the 15w40 because of the lifter design. I'm thinking that if the truck was still under any type of warranty, there would be an oil sample analyses to make sure the proper type of oil was used due to the expensive repair costs. If the truck is out of warranty, I still would not use the 15w40, just my opinion.

You mean a lifter design that’s prone to issues with deposits?

 

[Ruby]

You mean a lifter design that’s prone to issues with deposits?

I do not honestly know? Just an opinion on my part not a fact, I'm guessing the 10w30 or 5w40 is required on the 2019's and newer due to tolerances with new designs. If I had a 2019 or newer, I would not use the 15w40. I would follow the Cummins Guidelines.

 

[kschachn]

I do not honestly know? Just an opinion on my part not a fact, I'm guessing the 10w30 or 5w40 is required on the 2019's and newer due to tolerances with new designs. If I had a 2019 or newer, I would not use the 15w40. I would follow the Cummins Guidelines.

No it’s not tolerances. Oil molecules aren’t that large.

 

[Ruby]

No it’s not tolerances. Oil molecules aren’t that large.

Tolerances are indeed important regarding oil flow/protection on critical parts. There is a reason for example why the 2019 and Newer Rams are not to use the 15w40 Oil. From what I read, it's due to the new lifter design beginning in 2019.

 

[dnewton3]

The problem with this topic is that Cummins is painting a VERY broad brushstroke onto the topic of viscosity, when their stated concern is deposits. And honestly, it is providing really poor "coverage" of the concern. And whatever the underlying nature of their concern, it's also only applicable to later model engines (2019 and up).

Since when does viscosity directly address deposits anyway??? Anyone who's been here on BITOG long enough knows that viscosity has not nearly as much effect on cleanliness as does the additive package.

Seems like maybe HTHS might be a more appropriate way to address the vis topic, but obviously Joe Dirt doesn't know much about that, and it's impossible to get lube marketing folks to print this kind of stuff on a label; it's hard enough to get them to put it into a PDS. And again, it really doesn't address the topic of cleanliness DIRECTLY.

But what Cummins is doing is trying to tip the scales in their favor; they are presuming that 5w-40 lubes are "better" (typically requiring at least a group III stock) and will resist oxidation deposits a bit better than a lower tier base oil in some of those 15w-40 rated farm-fleet lubes. Further, many of the 5w-40 rated products are intended for longer OCIs, and so by their very nature, they may have a slightly more robust DI package. So Cummins is taking a round-about course in speaking to deposits by making some really lame implications via viscosity.

I find it incredibly odd that they approve the use 10w-30 rated oils; there's no real assurance that those lubes wouldn't leave deposits any more or less than a 15w-40. I've run 10w-30 HDEOs for years in my diesel applications; I'm not against that vis by any means. But I just find it odd that they approve a 10w-30 but not a 15w-40, when there's no generalized proof that either would be superior or inferior in terms of deposit control.

And as we all know, there are plenty of superior top-tier 15w-40 lubes from Amsoil, HPL, etc that would FAR exceed the cleanliness needs of any 15k mile OCI, over the T6 Rotella product that Cummins is touting.

 

[kschachn]

Tolerances are indeed important regarding oil flow/protection on critical parts. There is a reason for example why the 2019 and Newer Rams are not to use the 15w40 Oil. From what I read, it's due to the new lifter design beginning in 2019.

Actually not but it shows the confusion that has resulted from this poorly conceived document.

 

[Snagglefoot]

Cummins specs 5w40 and 10w30 in their new version of the 6.7 engine. Not to use 15w40 due to the hydraulic rollers on their lifters. My question is why 15w40 will damage the lifters and 5w40 will not if the oil is the same thickness at operating temperature? Or is 5w40 thinner at operating temperature and just has the protection of 15w40 weight oil?

Can you post the alleged instructions not to use 15w40 ?

 

[kschachn]

Can you post the alleged instructions not to use 15w40 ?

There are a couple of threads referencing the document but here is one. It’s all over the road in terms of actual technical reasoning but does seem to settle on deposit formation.

A winter rating in and of itself does not cause deposits.

Thread 'Stellantis 6.7L Cummins TSB: Only use 10W30 on 2019MY+, 15W40 can cause damage'

Jul 11, 2022

https://static.nhtsa.gov/odi/tsbs/2020/MC-10178698-9999.pdf

Was advised by a few reputable dealer techs than 15W40 was causing the pushrod and rocker arm issues, and this is one of the reasons why Stellantis came out with this TSB.

Any thoughts on this? Surprised to see a 15W-xx oil cause issues compared to a 5W-xx or 10W-xx in >0F conditions.

• The Critic
• Replies: 58
• Forum: Heavy Duty Engine Oil (HDEO) - Diesel Vehicles

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[Snagglefoot]

Here is the motor oil recommendation for the 2024 Ram diesel. You can make your own conclusions. They totally getting away from 15W. That’s grandpa’s oil.

 

[dnewton3]

Seriously ... this can only be interpreted one of two ways ...

1) the engineers at Cummins are stupid and don't understand lubes
2) the engineers at Cummins do understand lubes, but assume the buying public is stupid

Either way, it's just silly. Am I really supposed to believe that a 15w-40 will leave deposits that 10w-30 wouldn't? Especially if they were in the same product line (Rotella offers T4 in 10w-30 and 15w-40, for example). What does GRADE have to do with leaving deposits ??? So I'm supposed to believe that 5w-40 T6, and 10w-30 T4 or T5 or T6 would all be OK, but not 15w-40 T4 or T5 or T6?

Wow ... that's as stupid as it gets.

 

[Bighorn2500]

People are paying a good buck to convert those 2019 & newer back to flat tappet from hydraulic.

https://hamiltoncams.com/product/19...IxnKEI96GmCVdHkXcKgTpZTeoFl3PAcSkHE8c3_rgnTl1

 

[NiwradND]

Seriously ... this can only be interpreted one of two ways ...

1) the engineers at Cummins are stupid and don't understand lubes
2) the engineers at Cummins do understand lubes, but assume the buying public is stupid

Either way, it's just silly. Am I really supposed to believe that a 15w-40 will leave deposits that 10w-30 wouldn't? Especially if they were in the same product line (Rotella offers T4 in 10w-30 and 15w-40, for example). What does GRADE have to do with leaving deposits ??? So I'm supposed to believe that 5w-40 T6, and 10w-30 T4 or T5 or T6 would all be OK, but not 15w-40 T4 or T5 or T6?

Wow ... that's as stupid as it gets.

Now your thinking like I was when I started this post!

 

[johnmyster]

The problem with this topic is that Cummins is painting a VERY broad brushstroke onto the topic of viscosity, when their stated concern is deposits.

Actually not but it shows the confusion that has resulted from this poorly conceived document.

Deposits vs "but the lifters have tiny holes and startup flow"...

You could argue this until you're blue in the face on da cummins forums. Truck bros can't comprehend. Nobody knows how a hydraulic lifter actually works. World has lost its mind.

 

[OLEJOE]

Seriously ... this can only be interpreted one of two ways ...

1) the engineers at Cummins are stupid and don't understand lubes
2) the engineers at Cummins do understand lubes, but assume the buying public is stupid

Either way, it's just silly. Am I really supposed to believe that a 15w-40 will leave deposits that 10w-30 wouldn't? Especially if they were in the same product line (Rotella offers T4 in 10w-30 and 15w-40, for example). What does GRADE have to do with leaving deposits ??? So I'm supposed to believe that 5w-40 T6, and 10w-30 T4 or T5 or T6 would all be OK, but not 15w-40 T4 or T5 or T6?

Wow ... that's as stupid as it gets.

Well it wasn’t Cummins who came out with the TSB. It was Stelantis and they came out with it around May of 2020. I have seen a spreadsheet with a list of trucks with failed lifters and cams with only 1 truck listed as having been running 15-40 and it had 350,000 miles at the time of the failure. All of the rest of them, 20 or so, were running 10-30 or 5-40. Don’t know if the truck running 15-40 was ever started cold though.
The 5, 10 or 15 weight should only come in to play on cold starts.
Cummins only manufactures this engine for one application. Ram trucks. This engine is used in no other application. Parts for these engines can only be bought through a Mopar dealer. This isn’t the first time Ram/Stelantis has changed oil specifications for their diesel engines. I really don’t think they know what these engines need. They don’t know how to stop the frequent regen issues a lot of owners are having.

 

[NiwradND]

Still makes me wonder if 0w40 would be a better oil to use in alot of cases?

 

[Hohn]

Deposits.

FCA thinks running full syn will prevent the deposits formed when someone runs bargain basement conventional 15w-40 at their nonsense 15k OCIs.

They don't want you running conventional so they blanket banned all 15w-40. All the punters think it's because it's related to flow. It's not.

Pick a 5w-40 and stick with it. Delo, Delvac, Rotella, even Fram, etc.

I suspect this is exactly correct. FCA wants to advertise long ODIs and was concerned that cheap oils that can meet 15w-40 but not 5w40 would cause internal deposits in the hydraulic lifters.

It's just too hard to put in customer language something like "Oil must be API Group III or higher base."

 

[johnmyster]

I suspect this is exactly correct. FCA wants to advertise long ODIs and was concerned that cheap oils that can meet 15w-40 but not 5w40 would cause internal deposits in the hydraulic lifters.

It's just too hard to put in customer language something like "Oil must be API Group III or higher base."

I saw it stated well elsewhere. There are two kinds of lifter failures in these engines. Those that are lubricant related, and those that are lifter design related. FCA is trying to save face by acknowledging/addressing the lubrication related failures. Can lubrication cover for poor design/manufacturing? Probably not.