2021 Chevy Duramax L5P - 6,400 miles on oil/8,900 total vehicle miles - HPL 5w-40

wwillson

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This is a 2021 Chevy 3500 DRW L5P Duramax that pulls a 20,000 pound 5th wheel for a combined GVW of 29,000 pounds give or take a dog or two. The current sample has about 6,000 miles of towing and 400 miles of local sight seeing. I know that's not a very good towing vs sight seeing ratio, but there were a couple special purpose non-sight seeing trips towing the trailer. We'll do better in the future :) The fuel consumption towing was 650 gallons which yielded an average of 9 MPG, this engine works hard almost all the time. There where two trips through the tunnels on I-70 west of Denver. 50 MPH @ 2,100 RPM and 2 MPG on the way up and 35 MPH with exhaust braking at 3,500 RPMs on the way down.

The additional Fe in the oil was at a rate of 4.8PPM/1k miles and the Al was added at a rate of 2.3PPM/1k miles and is indicative of wear-in. The Si seems to be coming from engine seals or gaskets and has decreased considerably compared to the factory oil. The K is strange, but Glycol is NEG, so we'll just watch the numbers over time.

Lab is Wearcheck

Sample Information
Sample Date6/23/202107/17/202124 Aug 2021
Machine Age miles2,5002,7008,900
Oil Age miles2,5002006,400
Machine Time hours5562214
Oil Time hours557152
Filter Age miles2,5002006,400
Oil ChangedYesNoNo
Filter ChangedYesNoNo
Make-up oil000
BrandFactoryHPLHPL
Viscosity15-405w-405w-40
Wear Metals
Iron12436
Chromium<1<12
Nickel<100
Titanium<1<1<1
Silver3<1<1
Aluminum<1015
Lead612
Copper1092885
Tin610
Vanandium<100
Additives
Boron1201512
Barium<100
Molybdenum2514450
Manganese<1<1<1
Magnesium672995968
Calcium126024392414
Phosphorus100010991029
Zinc115511791148
Contaminants
Silicon873348
Sodium753
Potassium11243
Fuel %<1<1.0<1.0
GlycolNEGNEGNEG
Soot%0.10.10.4
Fluid Condition
TBN8.5514.913.3
Viscosity13.914.513.8
 
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Which HPL 5w40 was this? Looks like it already sheared a bit. That motor is definitely working. Potassium is interesting. Does the L5P have primary and secondary cooling systems like the PSD? Not familiar with the latest duramax. Curious as to if you have a small EGR cooler leak or head gasket (although I’ve never seen a duramax put coolant in the oil with failed HGs.)
 

dnewton3

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Indianapolis, IN
To me, this seems what I'd expect from the conditions of use ... The Fe and Al are from the engine working harder, and frankly, as young as the engine is, it's being "broken in" in an excellerated manner. Where a normal car engine may break-in over 20k or 30k miles of light commuting use, this engine is breaking-in very quickly, due to the loading. The Fe and Al are sourced from the cylinders and pistons. This is not uncommon when an engine is working much closer to it's limits. Pulling a much heavier RV with a much greater wind-resistance load will certainly work this engine. But, that's what it's made for, after all.

The K is interesting. Something to watch for. Not sure of the source, but since it's not in the virgin oil, then coolant is the most likely source. But why???
 

wwillson

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Which HPL 5w40 was this?
This is the "CK-4 HD Engine Oil" not the premium.

That motor is definitely working.
I will add that I tow at 65 MPH and with the 3:43 gears the engine runs at 1525 RPMs in 10th gear. This mill churns along all day at those RPMs and makes a lot of power. The trans mapping will let the speed decrease about 2 MPH going up a hill before it shifts into 9th. I've gotten good at turning off the cruise at the bottom of a steep hill and accepting a couple MPH decrease in speed climbing the other side and keeping the trans in 10th. It's very impressive to see how much torque this engine makes at just above an idle for some engines.
 
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NEBRASKA
Blackstone indicated some K on the two uoa from my LML, one of which I posted here. I have no idea where it is coming from.
 
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Kansas
I will add that I tow at 65 MPH and with the 3:43 gears the engine runs at 1525 RPMs in 10th gear. This mill churns along all day at those RPMs and makes a lot of power. The trans mapping will let the speed decrease about 2 MPH going up a hill before it shifts into 9th. I've gotten good at turning off the cruise at the bottom of a steep hill and accepting a couple MPH decrease in speed climbing the other side and keeping the trans in 10th. It's very impressive to see how much torque this engine makes at just above an idle for some engines.

Thanks for sharing your UOA numbers. Very interesting. I have a 2021 GMC 3500 and just sent off some oil for analysis after about 7000 miles of use. I will try to get that data posted for comparison. About half of my 7000 miles are towing a trailer around 5,500 lbs. I eventually plan to upgrade to a 5th wheel thus the vehicle choice.

Are you towing using the trailer mode? Even with my lighter trailer, my truck will often select 9th gear when using tow mode and climbing a modest grade and speeds between 60 and 65 mph. This happens much less as I stay at 65 or a bit more.
 

wwillson

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Are you towing using the trailer mode?
Yes, always as the trans mapping will use all 10 speeds instead of skip-shifting 1 & 3

The TCM seems to like 9th better than 10th for climbing hills, however you can fool it by turning off the cruise and accepting a couple MPH decrease while climbing, you'll use less fuel as well.
 
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Aug 8, 2004
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323
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NJ
I have a 2021 chevy 3500 with same engine in my hotshot fleet towing 24k to 26k gvw all the time that just crossed 105k miles on constant diet of cheapest 15w40 ck4 oil. Changes every 2 to 5 weeks. 6k to 15k miles depending on when driver gets back. Using no oil between changes which is great. I might grab a sample next time. Unit has about 3k hour on it now.
 
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To me, this seems what I'd expect from the conditions of use ... The Fe and Al are from the engine working harder, and frankly, as young as the engine is, it's being "broken in" in an excellerated manner. Where a normal car engine may break-in over 20k or 30k miles of light commuting use, this engine is breaking-in very quickly, due to the loading. The Fe and Al are sourced from the cylinders and pistons. This is not uncommon when an engine is working much closer to it's limits. Pulling a much heavier RV with a much greater wind-resistance load will certainly work this engine. But, that's what it's made for, after all.

The K is interesting. Something to watch for. Not sure of the source, but since it's not in the virgin oil, then coolant is the most likely source. But why???
I found high Al during winter use, repeated very cold starts and I use the exhaust brake a lot.
It took a few years (2011 LML) to get the Cu down to near zero.
Bully Dog'd 'n deleted the oil stays clean instead of turning black in 10 miles.
 
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