2021 Duramax L5P oil consumption cause and solution

[wwillson]

"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.

Are you sure? What did the marketing guys tell the engineers? I can imagine a conversation that went something like this, "Engineer says: We can show that running the engine at these high power levels will shorten the longevity. Marketing says: It doesn't matter, if we don't keep up with the torque race, it will badly hurt sales. Just keep turning the power up, we've calculated the number of hurt engines before the warranty ends and we will still be way ahead in profits. Just do it."

Maybe we are talking about two different issues. I'm talking about problem free longevity and you seem to be talking about catastrophic failure. We have already shown running with high EGTs will cause oil consumption and who knows what other long term issues. Borg Warner says the maximum continuous turbine inlet temperature for this turbo is 1472°F, I exceeded that by quite a bit. Not good for longevity. It can clearly be shown in UOA that if you run high EGTs the aluminum will increase per thousand miles. The aluminum is coming from the pistons, as the hotter they get, the softer they get. Not good for longevity. I choose to modify how it pull with my truck, because I'm concerned about longevity, not only for the engine, but also for the after treatment system, which is hurt by zinc, phosphorous, and ash from the consumed engine oil.

It can be argued that it's ok to run this engine at WOT and it won't blow up catastrophically and it can be argued that running it at WOT or very high power/heat levels will shorten the service life of the engine. We are both right.

 

[High Performance Lubricants]

Are you sure? What did the marketing guys tell the engineers? I can imagine a conversation that went something like this, "Engineer says: We can show that running the engine at these high power levels will shorten the longevity. Marketing says: It doesn't matter, if we don't keep up with the torque race, it will badly hurt sales. Just keep turning the power up, we've calculated the number of hurt engines before the warranty ends and we will still be way ahead in profits. Just do it."

Maybe we are talking about two different issues. I'm talking about problem free longevity and you seem to be talking about catastrophic failure. We have already shown running with high EGTs will cause oil consumption and who knows what other long term issues. Borg Warner says the maximum continuous turbine inlet temperature for this turbo is 1472°F, I exceeded that by quite a bit. Not good for longevity. It can clearly be shown in UOA that if you run high EGTs the aluminum will increase per thousand miles. The aluminum is coming from the pistons, as the hotter they get, the softer they get. Not good for longevity. I choose to modify how it pull with my truck, because I'm concerned about longevity, not only for the engine, but also for the after treatment system, which is hurt by zinc, phosphorous, and ash from the consumed engine oil.

It can be argued that it's ok to run this engine at WOT and it won't blow up catastrophically and it can be argued that running it at WOT or very high power/heat levels will shorten the service life of the engine. We are both right.

This ^^^^

 

[Astro14]

If it helps, we run our turbines at reduced power (less than max heat) for nearly every takeoff.

Even a few degrees below max makes a big difference in life.

 

[mattd]

I would still aim for my original suggestion for optimal longevity. JMO

 

[JHZR2]

If it helps, we run our turbines at reduced power (less than max heat) for nearly every takeoff.

Even a few degrees below max makes a big difference in life.

Same. Time at temperature (e.g., turbine inlet temperature) is a major determinant of life. Much of that is also corelated with fuel sulfur levels, since that results in accelerated hot section corrosion, which aren’t an issue here.

But reduced temperatures are a benefit.

 

[MaxPF]

Are you sure? What did the marketing guys tell the engineers? I can imagine a conversation that went something like this, "Engineer says: We can show that running the engine at these high power levels will shorten the longevity. Marketing says: It doesn't matter, if we don't keep up with the torque race, it will badly hurt sales. Just keep turning the power up, we've calculated the number of hurt engines before the warranty ends and we will still be way ahead in profits. Just do it."

Maybe we are talking about two different issues. I'm talking about problem free longevity and you seem to be talking about catastrophic failure. We have already shown running with high EGTs will cause oil consumption and who knows what other long term issues. Borg Warner says the maximum continuous turbine inlet temperature for this turbo is 1472°F, I exceeded that by quite a bit. Not good for longevity. It can clearly be shown in UOA that if you run high EGTs the aluminum will increase per thousand miles. The aluminum is coming from the pistons, as the hotter they get, the softer they get. Not good for longevity. I choose to modify how it pull with my truck, because I'm concerned about longevity, not only for the engine, but also for the after treatment system, which is hurt by zinc, phosphorous, and ash from the consumed engine oil.

It can be argued that it's ok to run this engine at WOT and it won't blow up catastrophically and it can be argued that running it at WOT or very high power/heat levels will shorten the service life of the engine. We are both right.

Automakers don't just concern themselves with the % of engines that make it out of warranty. They are concerned with long term reliability. They also balance that against performance levels and cost.

I'm not talking about catastrophic failure. I'm talking about B10 and/or B50 reliability. Duty cycles play a large factor in this. What percentage of overall run time is spent at WOT, even when towing? The answer is, not much.

The aviation guys talking about running their turbines at reduced power is a different matter. Engines on light duty trucks and cars spend most of their operation below 30% of their maximum output. Aircraft engines only run below 30% of their max output at ground idle and perhaps descent. Climb and cruise are what, about the 75% +/- 10% range? Im sure you pilots will correct me if Im wrong. Gas turbines also have much different degradation mechanisms compared to reciprocating engines. They are primarily time-limited by thermal degradation of the hot section components. For reciprocating engines the primary wearout mechanisms are due to actual wear of mechanical components. Mainly rings, upper cylinder, valves, and con rod bearings.

You say BW lists the max continuous TIT as 1472°. The key word there is CONTINUOUS. 1515° is only 43° above their continuous limit. Turbomachinery hot sections also typically have 30, 15, 5, and/or 1 minute ratings. Not every turbo has every one of those individual ratings, but the point is that they, like the pistons and valves, can tolerate progressively higher temps for shorter periods of time. Such excursions are duty cycle limited, so as an example if the turbine has a 5 minute rating of 1600°, that is 5 minutes per hour. Id bet that 1515° is within either the 30 or 15 minute envelope. I also bet BW doesn't publish that information. They do give it to the automakers, so the engineers can maximize the engines output within those limits.

In any case, its your truck and you are free to use it how you wish. If you really want to keep EGT's down, its a single EFI Live tune away. You will lose a significant amount of peak power, but the right tune can keep your EGT's below 1200°F.

The question is, if you are trying to maximize the life of the engine, who will be the beneficiary? Do you keep your trucks for 3,4, 500k+ miles? Or are you the type of person who trades/sells it after 100 or 200k miles?

 

[wwillson]

Automakers don't just concern themselves with the % of engines that make it out of warranty. They are concerned with long term reliability. They also balance that against performance levels and cost.

Of course

I'm not talking about catastrophic failure. I'm talking about B10 and/or B50 reliability. Duty cycles play a large factor in this. What percentage of overall run time is spent at WOT, even when towing? The answer is, not much.

Pulling long grades, close to WOT or WOT for sometimes miles. While pulling on the level in 10th gear, not WOT, but very high throttle positions, because you have to make a lot of power per power stroke when the engine is only running 1500 RPMs. The Duramax TCU will allow you to pull all day long every day in 10th gear with EGTs at 1250-1350F your engine will consume oil.

In any case, its your truck and you are free to use it how you wish. If you really want to keep EGT's down, its a single EFI Live tune away. You will lose a significant amount of peak power, but the right tune can keep your EGT's below 1200°F.

Or pull in eighth gear.

The question is, if you are trying to maximize the life of the engine, who will be the beneficiary? Do you keep your trucks for 3,4, 500k+ miles? Or are you the type of person who trades/sells it after 100 or 200k miles?

I will be the beneficiary.

I plan to keep this truck for a long time and we put a lot of miles/yr on. I would prefer not to have to make expensive repairs to the after treatment system, because I chose to pull in 10th and consumed many gallons of oil, filling the DPF with ash. Who knows about turbo longevity, exhaust valves and seats, coked ring packs, etc. Remember this engine spends most of it's life pulling and gets 9.5 MPG (6.2 GPH) while towing, that's working pretty hard.

My whole point is I can choose to pull in 10th or 8th. If I pull in 10th, my engine isn't going to blow up, but it will have to deal with a lot higher EGTs and that will eventually shorten the service life. By how much will it shorten the service life? Who knows and without a dyno and a lot of $, we will never know. GM knows, but they will never say. I would rather sell it at 400,000 miles and guess how much longer it would have run efficiently, than replace parts because I ran it at high EGTs. All speculation, but it is a fact that high heat shortens the service life of components.

 

[userfriendly]

I bought these new:
2006 LBZ, no exhaust brake, 6 speed 3500 CC/LB.
2011 LML w/exhaust brake, 6 speed 2500 XC/RB
2018 L5P w/exh brake, 6 speed 3500 CC/RB
all have 3.73 & 4x4 and 35s and run like new.

I pull steep mountain grades up to 14% in part throttle at 2,000-2,400 rpm, usually 4th or 5th gear depending on speed. In brake mode the LML and L5P engines see 3,000 rpm.
End of story.

 

[MaxPF]

Of course



Pulling long grades, close to WOT or WOT for sometimes miles. While pulling on the level in 10th gear, not WOT, but very high throttle positions, because you have to make a lot of power per power stroke when the engine is only running 1500 RPMs. The Duramax TCU will allow you to pull all day long every day in 10th gear with EGTs at 1250-1350F your engine will consume oil.


Or pull in eighth gear.


I will be the beneficiary.

I plan to keep this truck for a long time and we put a lot of miles/yr on. I would prefer not to have to make expensive repairs to the after treatment system, because I chose to pull in 10th and consumed many gallons of oil, filling the DPF with ash. Who knows about turbo longevity, exhaust valves and seats, coked ring packs, etc. Remember this engine spends most of it's life pulling and gets 9.5 MPG (6.2 GPH) while towing, that's working pretty hard.

My whole point is I can choose to pull in 10th or 8th. If I pull in 10th, my engine isn't going to blow up, but it will have to deal with a lot higher EGTs and that will eventually shorten the service life. By how much will it shorten the service life? Who knows and without a dyno and a lot of $, we will never know. GM knows, but they will never say. I would rather sell it at 400,000 miles and guess how much longer it would have run efficiently, than replace parts because I ran it at high EGTs. All speculation, but it is a fact that high heat shortens the service life of components.

The reason the TCU tries to keep your RPM in the 1500-1700RPM range is because that is the engines peak torque range. That range also coincides with the lowest BSFC. Every manufacturer tries to optimize fuel economy, because thats what the government mandates and that is what their competitors do. While higher pressures and temperatures accelerate wear, so does increased RPM.

If youre engine is consuming oil under what should be normal operating conditions, perhaps you need better oil? If I were a betting man Id say your oil loss under the conditions you describe is due to evaporation. That oil vapor is drawn out through the crankcase ventilation system, into the turbo inlet, and ultimately into the engine where it's burned. Oils may be considered fungible by the BITOG crowd, but they are not all created equal. Many don't specify the NOACK evaporation rating on the spec sheet, but with today's high power density light diesels they really should. Again, were I a betting man id wager that an oil with less evaporation would reduce or perhaps even eliminate your oil consumption issue when towing in 10th gear.

Since you are concerned with reliability and longevity more than the average owner, I would suggest paying close attention to your fuel system and fuel quality. If you are worried about being stranded and having expensive repairs, this is most likely the system that will be the culprit, The Bosch HP pump was a known failure item. On rare occasions an injector would stick open and burn down a piston. On the rarest occasions, the DMax is known to break crankshafts. GM has addressed all of these issues. They are using a Denso HP pump and Denso injectors on the L5P. Only time will tell if these components are more reliable and longer lived vs their Bosch counterparts. That said, unless and until it is proven that the HP fuel pump will last the life of the engine when running on non-additized #2 diesel fuel I would personally run a fuel supplement with known good lubricity additives. No pump ever died from having fuel with too much lubricity.

BTW, GM addressed the crankshaft issue by making the rod journals larger. They also finally followed International and Ford's engineering lead and are rolling the fillets on the L5P crank. Those changes should make DMax crank breakage a thing of the past, and prevent you from being a sad member of the DMax Crank Breaker's Club.

 

[wwillson]

The reason the TCU tries to keep your RPM in the 1500-1700RPM range is because that is the engines peak torque range. That range also coincides with the lowest BSFC. Every manufacturer tries to optimize fuel economy, because thats what the government mandates and that is what their competitors do. While higher pressures and temperatures accelerate wear, so does increased RPM.

Understood. It's pulling hard all day long at 1500 RPMs that causes high EGTs.

If youre engine is consuming oil under what should be normal operating conditions, perhaps you need better oil? If I were a betting man Id say your oil loss under the conditions you describe is due to evaporation. That oil vapor is drawn out through the crankcase ventilation system, into the turbo inlet, and ultimately into the engine where it's burned. Oils may be considered fungible by the BITOG crowd, but they are not all created equal. Many don't specify the NOACK evaporation rating on the spec sheet, but with today's high power density light diesels they really should. Again, were I a betting man id wager that an oil with less evaporation would reduce or perhaps even eliminate your oil consumption issue when towing in 10th gear.

Yes, I've stated that high piston crown temps lead to evaporative loss. I run HPL, you won't find a better oil.

I would personally run a fuel supplement with known good lubricity additives.

I do this.

 

[PiperOne]

..... They also finally followed International and Ford's engineering lead and are rolling the fillets on the L5P crank.....

It's kinda funny, GM knew this a long time ago. The old 6.5L diesels had rolled fillets.

 

[MaxPF]

Yes, I've stated that high piston crown temps lead to evaporative loss. I run HPL, you won't find a better oil.

So you're 100% positive no other oil would exhibit less evaporation loss under the same operating conditions?

 

[MaxPF]

It's kinda funny, GM knew this a long time ago. The old 6.5L diesels had rolled fillets.

So did the 4.3L V-6, the 3.8L V-6's from the Buick Grand National to the series I, II, and III engines, and all Gen 3, 4, and 5 small blocks with cast cranks. The 6.2L diesel was the first GM engine that I'm aware of that had rolled fillets. It debuted in 1982, and using rolled fillets allowed them to successfully use a cast nodular iron crank without having fatigue failure issues. You would think that the use of rolled fillets in so many engines and their impressive record of success would've encouraged their use in the DMax cranks as soon as fatigue-induced crank breakage began occurring at a significant rate. It's certainly not an expensive operation to perform in production.

 

[wwillson]

So you're 100% positive no other oil would exhibit less evaporation loss under the same operating conditions?

We are pretty darn sure. HPL products are known to this community to use high quality base oils and extremely robust add packs. The likelyhood that another diesel oil would perform better than HPL in my application is nil.

 

[MaxPF]

I'd like to see what the NOACK evaporation loss looks like on that oil. I can see from your mileage that the HPL is the only oil you have used, so you cannot realistically say "The likelyhood that another diesel oil would perform better than HPL in my application is nil".

 

[High Performance Lubricants]

I'd like to see what the NOACK evaporation loss looks like on that oil. I can see from your mileage that the HPL is the only oil you have used, so you cannot realistically say "The likelyhood that another diesel oil would perform better than HPL in my application is nil".

Wayne has been to our plant several times. He has seen TGA data showing evaporative loss of our oil vs. well known and widely used diesel oils. He has the confidence that works for him.

We are not people that trash competing products. There are plenty of decent oils on the market. If you prefer another you should use it.

Wayne is a very thorough individual. If you are questioning that you don’t know him very well.

David

 

[PiperOne]

I've been to the plant that makes Chicken McNuggets, doesn't make me a food expert.

I don't think we're questioning Wayne so much as we are the oil or a possible problem with his truck. I asked for input on the Duramax Forum and have asked several professional RV haulers with 2020+ L5P trucks. Every response so far is they leave the truck in 10th gear and let it do what it wants, and ....no reports of oil use across a wide variety of oil brands. This has been my experience as well with my 22 L5P.

 

[Deleted member 89374]

@High Performance Lubricants - does the quality of Diesel fuel, which at times is questionable, have an impact on oil consumption in a Diesel engine? I don't see fuel quality being discussed very often, if at all.

 

[wwillson]

I've been to the plant that makes Chicken McNuggets, doesn't make me a food expert.

I don't think we're questioning Wayne so much as we are the oil or a possible problem with his truck. I asked for input on the Duramax Forum and have asked several professional RV haulers with 2020+ L5P trucks. Every response so far is they leave the truck in 10th gear and let it do what it wants, and ....no reports of oil use across a wide variety of oil brands. This has been my experience as well with my 22 L5P.

I saw your thread at DMaxforum: https://www.duramaxforum.com/threads/for-those-towing-heavy-with-2020-and-up.1026307/post-12493998

This particular post was the only guy that was pulling a heavy 5th wheel (tall) with a GCW of (28.5k) and he is using about 1/2 quart/1k miles. I have a GCW of right at 30k and pull a tall (13') 5th wheel. It takes serious power to pull heavy and tall, especially into the wind. He should try lowering the sustained EGTs by pulling his 5th wheel in 8th or 5th if he has a six speed.

Another poster said, "If that is true, it would make me think turbo seal is bad. He would be running higher boost in 10th vs 8th". This is flat wrong, you don't run higher boost when pulling in 10th, you run higher boost pulling in 8th, but not by more than 1 psi. There simply is no substantial difference.

Most of the replies in your post don't pull heavy and tall. It's like comparing apples to oranges. I used to pull an Airstream and got 14 MPG. When I pull my 5th wheel I get 9.5 if there isn't a headwind. Pulling into a headwind sucks fuel, I've averages as low as 7 MPG at 55 MPH.

@Doug Hillary used to measure work by how much fuel an engine consumed, I think it fairly applies here as well. If we are going to compare who uses oil and who doesn't, their averages fuel consumption should be close to mine.

 

[MaxPF]

Wayne has been to our plant several times. He has seen TGA data showing evaporative loss of our oil vs. well known and widely used diesel oils. He has the confidence that works for him.

We are not people that trash competing products. There are plenty of decent oils on the market. If you prefer another you should use it.

Wayne is a very thorough individual. If you are questioning that you don’t know him very well.

David

OK, so, what is the NOACK evaporation on the product he is using?