2021 Duramax L5P oil consumption cause and solution

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I have a 2017 Duramax L5P with a Banks Derringer that I run on level 6 all the time. I tow a 15k fifth wheel and sometimes have another trailer behind it depending on what I am wanting to do. My 17 has a smaller oil cooler than the OP 2020 and Gale Banks did a comparison of the two several years ago, and he actually offers a kit to upgrade the earlier L5P to the newer oil cooler. That being said, when working the engine hard with high EGT's the engine oil is squirted onto the bottom of the piston to help transfer piston heat to the oil. If oil temps gets much above 220 degrees you better back off because the oil is getting too hot and consumption can go up. I only run 5W40 in the winter when it gets very cold and I can't plug in the block heater because 15W40 offers more protection that 5W40 in most oils. That being said, head winds are a pain, fuel economy drops like a rock and EGT's get much higher because of the increased engine load. I two will drop gears to keep my EGT's in check. I typically drive with my instant fuel economy pulled up on my dash and I will pull the highest gear that gives me the best fuel economy. My engine has on occasion used a little oil, but probably because I worked the engine very hard and got the oil temp too hot. I run 5000 mile oil change intervals and use a good quality 15/40 most of the time. In the last year oil brands have been hard to pin down, but I usually have a years worth on the shelf.
 
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If you can somehow get your dealer to put you in touch with a zone rep I would pose the question to him/her and then ask for it to be kicked up the chain to current product engineering. You would probably need to vet whoever responds to make sure they arent just passing you off on some low level customer service functionary. Youre going to need to climb the food chain to get an actual answer from someone with the knowledge.
Anything less than that is anecdotal.

After using a scan gauge on my 2005 LLY D-max I found that the truck would often stay in 5th gear when it actually would have run more efficient with lower EGT's in 4th. After finding this info years ago I always felt the truck up-shifted quicker than I wanted when towing.
I spent some time talking with an really smart guy today about the “static momentum” of really large companies. They made their money and lost their competitive edge. The market is something millions watch on TV on Sundays, and one of the Big 3’s top engineers steered this customer to Mobil.

Long story short, there was no improvement. A call to the guy in question and a week of development, followed by a month of real-world testing showed they had a fix for something Mobil couldn’t/wouldn’t.

@wwillson you know who I’m talking about, he’d be my first contact for the “why” and the resolution.
 
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Not sure what your post has to do with my comments. Its a little too cryptic for me to follow.
Sorry, got sidetracked. You had mentioned contacting GM, and my point there was that most of the people involved at the corporate levels are either bound by contract or “tribal knowledge” or ignorance, and will simply repeat an official line- like if you called Chrysler about oil for the Dodge Demon, they’re going to tell you 100% of the time to use the Pennzoil 0w40. There’s no outside the box thinking or real understanding in their answer; they aren’t the lubrication engineers nor even in the lubrication industry. They regurgitate what they’re told- but on the flipside, this board does have several contacts inside the lube industry itself and can take a specific application and good feedback to these people and get a much more appropriate lube… does that clear it up? 👍🏻
 
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I understand now. Part of your point is why I originally mentioned vetting the people that someone is in contact with. Like any other organization, GM has many very dedicated folks that work very hard to resolve issues. (and probably a few duds too, thats the problem with hiring humans)

Thanks.
 
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The data point is EGT1/1, which is the hottest exhaust sensor in the Duramax and my assumption the sensor is in or close to the manifold. I wish someone could tell me exactly where the sensor is, because I can't find any information, even googling. The rest of the exhaust sensors are post turbo (man is this interesting to watch) and at four other points in the after treatment system. All of the exhaust sensors are much cooler than EGR1/1.

I've read that too. The Duramax pulling in 10th will maintain > 1200°F all day long under the right conditions. Those sustained temps can't help longevity, but the marketing folks sure to like the torque war.

Not sure if you already found where EGT temp sensor 1 is, but according to my service info it's located "right front engine compartment, in exhaust, in front of Diesel Particulate Filter differential pressure sensor".
 

wwillson

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Not sure if you already found where EGT temp sensor 1 is, but according to my service info it's located "right front engine compartment, in exhaust, in front of Diesel Particulate Filter differential pressure sensor".
EGT1 is post the diesel oxidation catalyst just behind the turbo and in front of the diesel particulate filter. Sensor "EGT" is much hotter than EGT1, so it must be in the manifold or pre-turbo.

This is where I believe the sensors are:

Manifold => EGT => Turbo => EGT1 => DOC => EGT2 => DPF => EGT3 => EGT4 => SCR => EGT 1/5

I wish someone could tell me if I'm correct.
AB069943-A46B-4FEB-BD3A-C14AA2D1C719.jpeg
 
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EGT1 is post the diesel oxidation catalyst just behind the turbo and in front of the diesel particulate filter. Sensor "EGT" is much hotter than EGT1, so it must be in the manifold or pre-turbo.

This is where I believe the sensors are:

Manifold => EGT => Turbo => EGT1 => DOC => EGT2 => DPF => EGT3 => EGT4 => SCR => EGT 1/5

I wish someone could tell me if I'm correct.
View attachment 130936

That's odd... I didn't see any other EGT sensor in the literature. No wonder you're having a tough time finding it!
 
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It’s got to be either in the EGR inlet tube from the exhaust manifold or in the up pipe to turbo pipe or possibly but unlikely exhaust manifold. Those are the hottest areas in the exhaust
 

wwillson

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It’s got to be either in the EGR inlet tube from the exhaust manifold or in the up pipe to turbo pipe or possibly but unlikely exhaust manifold. Those are the hottest areas in the exhaust
I believe it's in the EGR inlet tube...
 
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The poster who said 1250° EGT is the max isn't entirely correct. That was/is the case for the 12V Cummins, as well as the 24V with the VP44 IP. When Cummins went to common rail they redesigned the block and eliminated the oil squirters from the main saddles, relocating them to above the pan rails with a dedicated galley to feed them. The pistons on CR engines actually have an oil channel in them, and the newer style oilers literally enter an opening in the piston at BTC to flush a bunch of cooling oil through that channel. This has two effects: it raises the allowable EGT while keeping piston crown temps in check, and it reduces skirt expansion.

Needless to say, the Cummins isn't the only engine with oil channels in the pistons for maximum cooling. All modern diesels have these features. As a result, EGT's can be run higher which allows more power to be made at a given boost level. As long as the factory EGT limit isn't exceeded, longevity shouldn't suffer.

So, what IS the factory EGT limit? Well, unless GM actually publishes such info, the only way to know is to put a pyrometer on a completely stock engine. The hottest temps you see will be within the factory EGT limit, because they tune them to keep it within their limits. They don't want to be replacing engines. Doing so under warranty is expensive, and doing so even out of warranty gives the brand a black eye. Engines with aftermarket tunes can, and usually do, exceed these limits in order to make more power. Thats why using an aftermarket tune automatically voids the powertrain warranty.
 

wwillson

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This is the EGT and other day pulling Raton Pass. I kept the EGT <= 1350°F at a speed of about 50 MPH for a few minutes, then I held it at wide open throttle for about 15 seconds. This is the heat the L5P is capable of generating. I didn't have the guts to maintain WOT to see when/if the computer would say enough is enough. The 1515°F EGT is the hottest I've ever seen and is way too hot to sustain without melting pistons. The charge air cooler inlet was 414°F, which is 89°F hotter than I've ever seen. Pretty impressive that the charge air cooler removed 312° of heat from the boost coming off the turbo. The maximum boost I've seen a much lower elevations 28.2, 25.2 was all the turbo could muster at 7,800'

I'm still pulling in 8th gear at 1,880 RPM with an average EGT of about 875°F and zero oil consumption.

875F6BF2-C33D-4657-9A66-811A185E20B9.jpeg
 
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This is the EGT and other day pulling Raton Pass. I kept the EGT <= 1350°F at a speed of about 50 MPH for a few minutes, then I held it at wide open throttle for about 15 seconds. This is the heat the L5P is capable of generating. I didn't have the guts to maintain WOT to see when/if the computer would say enough is enough. The 1515°F EGT is the hottest I've ever seen and is way to hot to sustain without melting pistons. The charge air cooler inlet was 414°F, which is 89°F hotter than I've ever seen. Pretty impressive that the charge air cooler removed 312° of heat from the boost coming off the turbo. The maximum boost I've seen a much lower elevations 28.2, 25.2 was all the turbo could muster at 7,800'

I'm still pulling in 8th gear at 1,880 RPM with an average EGT of about 875°F and zero oil consumption.

View attachment 135549
Whoaa, thats hot! You might be still under warranty, but that makes me wonder if it needs an aftermarket tune! Would being rich at that rpm cause that?

Would a free flowing exhaust help at all ?
 
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wwillson

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Whoaa, thats hot! You might be still under warranty, but that makes me wonder if it needs an aftermarket tune! Would being rich at that rpm cause that?
My opinion is that this level of heat is a product of the torque race between Ford, Chevy, and Dodge. The Duramax is 404 cubic inches (6.6L) and can produce 910Lb/ft of torque an 445 HP, that's a lot. It takes a lot of heat to make that much power. If this engine were in a continuous power application, like a tractor pulling a tillage implement, it would probably be putting out 175HP and have sustained EGTs of < 1000°F at WOT. In a tractor an engine is expected to last at least 5000-7000 hours between overhauls. If you ran the Duramax at WOT at 445HP, the engine life would be short.

We've already seen this engine is capable of making so much heat that it uses oil because of the high EGTs. The "My torque is bigger than your torque" is hurting engines, guaranteed. Not blowing up, but shortening their service life.
 
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This is the EGT and other day pulling Raton Pass. I kept the EGT <= 1350°F at a speed of about 50 MPH for a few minutes, then I held it at wide open throttle for about 15 seconds. This is the heat the L5P is capable of generating. I didn't have the guts to maintain WOT to see when/if the computer would say enough is enough. The 1515°F EGT is the hottest I've ever seen and is way too hot to sustain without melting pistons. The charge air cooler inlet was 414°F, which is 89°F hotter than I've ever seen. Pretty impressive that the charge air cooler removed 312° of heat from the boost coming off the turbo. The maximum boost I've seen a much lower elevations 28.2, 25.2 was all the turbo could muster at 7,800'

I'm still pulling in 8th gear at 1,880 RPM with an average EGT of about 875°F and zero oil consumption.

View attachment 135549

If that is on a stock tune, then its safe. As I said, the Duramax is a modern engine with oil cooled channels in the piston. A 1500°F EGT doesnt mean the piston crown is getting that hot. There are many factors that determine how much heat the piston crowns actually see, and more factors that determine the actual piston crown temps. Again, GM will NOT allow the piston crown temps to get high enough to do damage.

Also don't forget that gasoline engines see even higher EGTs than this. The gas density is lower, and the combustion chamber is in the head rather than the piston, but still the temps are there and the piston sees a large heat load. Most modern gasoline engines are now equipped with piston oil squirters due to higher power levels.
 
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"Safe" means GM powertrain engineers have run these engines for hundreds of hours on dynos at WOT, then tore them completely down and did all sorts of analysis on the components to ensure the engine will be reliable at that power level.
 
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