CAT HEUI Shearing Oil Down?

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Subject truck is a 2006 Freightliner M2 with Cat C7 engine, 11293 kms on the oil. Engine has a deep sump, holding 28 l of oil. Last fill was in December 2016. The viscosity is down to 12.9. On another truck ( 1999 Freightliner FL70 with Cummins ISB 5.9, 6500 kms on oil ) with the same Delvac ESP 0W40 fill, the viscosity is 14.4.

I usually change the oil out at 8000 kms. This time I let it go longer, mostly because I expected the synthetic Delvac to last longer.

Is this 12.9 vs 14.4 significant? Should I not exceed the 8000 km change interval? Should the synthetic oil have not sheared down as quickly?
 
Cat's had HEUI for a fairly long time; not sure what they are currently produced with though.

Vis is only an input. If your wear metals are fine, then vis is only a reason to stay tuned in, not flush out.
 
The C7 changed over to common rail in 2007.

"vis is only a reason to stay tuned in, not flush out" I don't follow you. Are you saying that the oil did not need to be changed? The wear metals are fine as you can see for yourself from the analysis results. My concern on this engine is the fragile and very expensive HEUI pump and injectors. HEUI systems are known for shearing the oil down, hence my attention to viscosity. I do not want the HEUI system to suffer damage from sheared oil.
 
Was more of a general statement.

There are inputs and outputs to track. Outputs such as wear metals are the most important info you'll get from a UOA, because it speaks directly to how things are wearing. In contrast, inputs (vis, FP, soot, TBN/TAN, etc) are all inputs; these can predict how much longer a lube MIGHT be able to survive in service, but they are only predictors and NOT reasons in-and-of themselves, to OCI.

Seen it so many times over the years; lube that is giving good wear traits is dumped prematurly simply because some arbitrary limit is reached. TAN crosses over TBN; so what? FP is lower than desired; who cares? Vis is below some industry standard; why panic? Until wear rates are affected, these are only cautionary indicators that should trigger one not to OCI, but simply to pay closer attention to the wear trend data.

In regard to HEUI, it's a common phenomenon that it will shear lubes down. But when viewed with more detail, it's common that HEUI will shear down thicker lubes quickly, but thinner lubes little, if any. We've seen this in countless 7.3L and 6.0L PSD UOAs. Vis will drop precipitously, but the wear metals go unaffected. Those who feed HEUI a typical 15w-40 will see significant shearing in as little as 3k miles at times, whereas those who use 10w-30 won't see much over 7.5k miles. It's like the HEUI simply prefers a thinner grade. And despite the grade differential, the wear rates seemingly go unaffected. Admittedly C7 UOAs are rare contrasted to the light-duty PSD UOAs we see proliferated here, but the contextual basis is the same.

What data do you have that shows a drop in vis is DIRECTLY responsible for HEUI failures? I've not seen any data to support such a claim. I've read plenty of internet rhetoric over the years about the fears of such, but I have yet to see any study data or methodical tear down data that shows grade thinning is the culprit. Typically contamination is the number one thing that kills pumps and injectors, not lube vis. I will grant you that at some point, oil could conceivably be too thin because it's gone way out of grade; perhaps fuel contamination has thinned lube WAY out of spec. But that's not "normal" shearing due to HEUI we're talking about here ...
Unless you can show me data (with clear causation and not just correlation) that reveals a DIRECT relationship between oil vis and HEUI longevity, I'm just not convinced that vis is something to get all worked up over.


My point is to not dump a lube load simply because some input condition trips your mental trigger. Let the wear data tell you when to OCI, not your preconceived notion as to some arbitrary limit. You already said it yourself; the wear metals are fine. So why dump oil?
 
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I have absolutely no proof that the sheared oil adversely affects The HUEI system. But I have come across many instances where Cat engine owners and Cat mechanics recommend oil change intervals to not exceed 6 to 8k miles on HUEI equipped engines, so that is what I have been doing.

Keep in mind that the HUEI system is only a small part of the entire engine, so wear in the HUEI system might not produce big wear metal numbers in a UOA.
 
Originally Posted By: dnewton3
Was more of a general statement.

There are inputs and outputs to track. Outputs such as wear metals are the most important info you'll get from a UOA, because it speaks directly to how things are wearing. In contrast, inputs (vis, FP, soot, TBN/TAN, etc) are all inputs; these can predict how much longer a lube MIGHT be able to survive in service, but they are only predictors and NOT reasons in-and-of themselves, to OCI.

Seen it so many times over the years; lube that is giving good wear traits is dumped prematurly simply because some arbitrary limit is reached. TAN crosses over TBN; so what? FP is lower than desired; who cares? Vis is below some industry standard; why panic? Until wear rates are affected, these are only cautionary indicators that should trigger one not to OCI, but simply to pay closer attention to the wear trend data.

In regard to HEUI, it's a common phenomenon that it will shear lubes down. But when viewed with more detail, it's common that HEUI will shear down thicker lubes quickly, but thinner lubes little, if any. We've seen this in countless 7.3L and 6.0L PSD UOAs. Vis will drop precipitously, but the wear metals go unaffected. Those who feed HEUI a typical 15w-40 will see significant shearing in as little as 3k miles at times, whereas those who use 10w-30 won't see much over 7.5k miles. It's like the HEUI simply prefers a thinner grade. And despite the grade differential, the wear rates seemingly go unaffected. Admittedly C7 UOAs are rare contrasted to the light-duty PSD UOAs we see proliferated here, but the contextual basis is the same.

What data do you have that shows a drop in vis is DIRECTLY responsible for HEUI failures? I've not seen any data to support such a claim. I've read plenty of internet rhetoric over the years about the fears of such, but I have yet to see any study data or methodical tear down data that shows grade thinning is the culprit. Typically contamination is the number one thing that kills pumps and injectors, not lube vis. I will grant you that at some point, oil could conceivably be too thin because it's gone way out of grade; perhaps fuel contamination has thinned lube WAY out of spec. But that's not "normal" shearing due to HEUI we're talking about here ...
Unless you can show me data (with clear causation and not just correlation) that reveals a DIRECT relationship between oil vis and HEUI longevity, I'm just not convinced that vis is something to get all worked up over.


My point is to not dump a lube load simply because some input condition trips your mental trigger. Let the wear data tell you when to OCI, not your preconceived notion as to some arbitrary limit. You already said it yourself; the wear metals are fine. So why dump oil?



I was going to mention exactly this. Many guys use a 10w30 since that's what the HEUI system shears it down to. This grade of oil must be closer to the tolerances of the HEUI system, hence the limited shearing with the thinner grade.
 
Originally Posted By: George7941
I have absolutely no proof that the sheared oil adversely affects The HUEI system. But I have come across many instances where Cat engine owners and Cat mechanics recommend oil change intervals to not exceed 6 to 8k miles on HUEI equipped engines, so that is what I have been doing.

Keep in mind that the HUEI system is only a small part of the entire engine, so wear in the HUEI system might not produce big wear metal numbers in a UOA.



I suspect the "recommendations" you get are based on nothing more than a fear of the unknown. That "unknown" being the presumption that vis has a direct relationship to HEUI systems wearing out. I've never seen any data to prove this relationship exists. I think the common factor is one of the mistaking correlation for causation. It kind of goes like this:
- thicker lubes are, and most certainly have been previously, the predominant grade of choice
- HEUI systems have had some history of wear failures
- thicker lubes do shear down with HEUI
And so people presume that correlation of shearing must be causing the wear. However it is completely unproven to be true.

Don't think of shearing being the issue; just think of grade itself. If thinner grades were a problem, then all HEUIs would exhibit the wear issues. But that's not the case.
In the PSD world, there are some folks who have faithfully used 10w-30 and have never had HEUI issues. Of note is RR1, but he's not alone.
On the opposite side of things, are we to believe that folks who've religiously changed 15w-40 at shorter intervals in their C7 have never, ever experienced HEUI failure? I think that's absurd to assume as well. IOW - if you did change 15w-40 often, are you 100% assured that you'll never have HEUI problems?


I agree that the wear from the HEUI components will be so low that even if there's a problem, it probably won't be easily seen in a UOA. However, and I admit I'm not intimately familiar with the C7 HEUI system we discuss here, what specifically is the failure mode of HEUI anyway? Are the issues similar to PSDs?
Here's a list of the common HEUI issues in the PSDs (7.3L and 6.0L)
- broken springs (nothing any grade of oil will cause nor stop from happening)
- poor connectivity (top end signal loss via bad/broken wiring looms or coils in the injector circuit; again no oil is going to cause or alleviate this)
- stiction (a thinner grade here can only help, not hurt)
- HPOP failure (typically a seal that goes bad as the pump really does not wear out, but fails to provide full pressure; this causes hard starting and poor idling)
- HEUI driver failure (in a 6.0L Ford, it's often referred to as the FICM; typically fails in the control unit due to heat/stress cycle failure; nothing to do with lubes)

And don't forget that all injectors do wear out eventually; it's not like this is an unknown phenomenon. Heck, every major city has at least one diesel injection rebuild service. Old IDI systems had wear, and they had the benefit of HIGH sulphur content. Common rail systems eventually wear out their pumps and injectors. CP3 pumps wear. P-pumps wear. Dmax injectors wear. Nothing lasts forever. The best thing for long life of pumps/injectors is clean fuel, and in the case of HEUI, clean oil. I've seen no evidence that thick vis will make a HEUI last longer.


What I'm saying is that rhetoric can run long and deep, and assumptions that are made end up turning into garage maintenance practices.
I am more than willing to accept that grade may cause HEUI issues, but I'd want to know the SPECIFIC mode of failure, and see DIRECT proof of how causation takes place in regard to vis.
Until then, label me a skeptic.


I understand your concern; you want a long, healthy run for your C7. Everyone wants a good ROI with long life from their equipment. And so, you've stuck with what you've heard; the mythology is that vis loss causes HEUI issues. I'm not taunting you; rather, just wanting to have you either be able to prove to yourself that the information you've heard is true, or false. Set emotion aside and look for the existence (or lack thereof) of real proof.


Next time someone tells you that vis drop causes HEUI failures, ask them to be very specific and state what component failed, how it failed, and why vis loss caused failure. If they cannot express this in a logical sense, it's just hooey.

You've got to decide if the smoke from this fire is legitimate, or is it just some darn foolish arsonist fanning the flames of ignorance, perpetuating the regurgitation of countless rumors?

I'm not saying what you claim it wrong. I just have never been convinced that it's true. The proof of data, and the logic of sound principles, is completely lacking.




.
 
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My understanding is that the weakest part of the Cat C7 HUEI system is a bearing in the HUEI pump which grenades and sends metal all through the fuel system and necessitating replacement of all six very expensive injectors.

I am doing my best to watch for signs of impending bearing failure - inspecting the magnetic oil drain plug, cutting the filter open and UOAs. If I see evidence of impending failure, I can just replace the HUEI pump and hopefully not have to replace the injectors.

Re injectors wearing out, we have a 1999 Freightliner at work with the Cummins 5.9 and, at 15000 engine hours, still has the original injectors. I add two stroke oil to the diesel at every fuel fill up.
 
Cat & International worked together making the HEUI system exist. There were some Cat engines they back-specced to 10w-30 due to viscosity shearing out of grade and cold/start issues. I had several Powerstrokes (7.3's & 6.0's) with the HEUI system and experienced the same shear issues with 15w-40/5w-40 you have experienced. Your wear metals look to be fine at your OCI.

I finally came to the conclusion it was a waste for me to run synthetic as it sheared out of grade, it cost more, extended drain intervals were out of the question, and wear metals were actually higher than with 10w-30.
 
Originally Posted By: George7941
My understanding is that the weakest part of the Cat C7 HUEI system is a bearing in the HUEI pump which grenades and sends metal all through the fuel system and necessitating replacement of all six very expensive injectors.


That in mind, I doubt any grade selection (10w-30 vs. 15w-40) will ever make that issue go away. Even if the thicker grade could delay it, it would probably be immeasurable in terms of time difference.

As you say, you can try to look for signs of impending doom. However, it may be more prudent to simply ask some respected CAT services what the average life-expectancy is for the pump, and change it prior to that degradation culminating into catastrophe. The risk being that unless you have a very good sense of being able to detect the onset of failure, it may be "too late" by the time you happen to discover it.
 
I think I will from now on just prophylactically replace the HEUI pump every three years instead of waiting for its demise and consequent damage to the rest of the fuel system.

The Jan 2013 and the Nov 2015 UOAs were done when the HEUI pump blew up and, as you can see, there is nothing in the UOA numbers indicating any issues.
 
Originally Posted By: roadrunner1
Cat & International worked together making the HEUI system exist. There were some Cat engines they back-specced to 10w-30 due to viscosity shearing out of grade and cold/start issues. I had several Powerstrokes (7.3's & 6.0's) with the HEUI system and experienced the same shear issues with 15w-40/5w-40 you have experienced. Your wear metals look to be fine at your OCI.

I finally came to the conclusion it was a waste for me to run synthetic as it sheared out of grade, it cost more, extended drain intervals were out of the question, and wear metals were actually higher than with 10w-30.


100% agree with everything said here. I had an '06 Powerstroke with the 6.0L just like RoadRunner, and mine also sheared the nuts off any 40-weight oil (in less than 3k miles nonetheless). I made the switch to a 10w30 as well, and the shearing slowed dramatically. Cold starts were better (at any temperature), and the injectors generally seemed happier. I would double check CAT's recommendations for your specific engine, because as RoadRunner said - they back spec'd 10w30 to cover a wide range of their HEUI systems.
 
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