OCI, not when but why?

[Atlas]

12 hours ago, Chuck FB said:

 

This comment dives into what a youtube channel called DemonWorks who is a GM mechanic that works a lot on the 3.0 engine at his day job but also has owned numerous personal 3.0 trucks and he had done UOA with a variety of 0W-20 oil brands and then switched it up to a 5W-30 on his current truck and I believe he generated a couple of 5W-30 tests and so far there was certainly a statistical drop in wear metals. I think now he is trying a 0W-30 for the winter and so those UOA's are yet to be generated. One thing is for sure, it takes time to create UOA's with a daily driver and the odd long distance trip within that at times, there is no instant gratification "answer" like a person would desire as of course owners of the 3.0 intently watching his results want answers now so they can make a possible better oil choice now, not years from now and I can understand that. Collecting good quality long term data is not a five minute gratification process but that is a statement your more than well aware of !, its a statement I mention for others reading my post. 

 

Admittedly, I'm a DemonWorks skeptic. He is a tech and who also has experience with his own trucks. I have yet to see anything beyond his own anecdotal experience and providing information about the 3.0 diesel which is easily obtained.

 

I'm keeping an open mind, but the few Youtube videos I've watched I've actually become nauseous (lack of image stabilization on his cameras) and have not learned anything I did not already learn from other sources.

[diyer2]

Shorter OCI's with better oil, not off the shelf oil, problem solved IMO. You know I like Amsoil.

[OnTheReel]

37 minutes ago, Atlas said:

 

Admittedly, I'm a DemonWorks skeptic. He is a tech and who also has experience with his own trucks. I have yet to see anything beyond his own anecdotal experience and providing information about the 3.0 diesel which is easily obtained.

 

I'm keeping an open mind, but the few Youtube videos I've watched I've actually become nauseous (lack of image stabilization on his cameras) and have not learned anything I did not already learn from other sources.

At around 13:00 he addresses high viscosity oil in the 3.0 diesel and the wear reduction.

[Grumpy Bear]

44 minutes ago, OnTheReel said:

At around 13:00 he addresses high viscosity oil in the 3.0 diesel and the wear reduction.

 

I'd say Geeks' video validated every thing I've ever said.

Guess it just needed to be said by someone else.

I'm good with that. 

 

[customboss]

1 hour ago, OnTheReel said:

At around 13:00 he addresses high viscosity oil in the 3.0 diesel and the wear reduction.

GM 3.0 diesel? He never says. What 3.0? European? Soot loading is NOT an issue in modern diesels. Lake mixes up gasoline engines with diesel engines. 
 

The video proves nothing about the GM 3.0 diesel using whatever vis you decide above 9 cSt @ 100c 

 

Again Grumpy and anyone that decides to run more viscous oil in your new under warranty GM 3.0 TD and show the results. 

[customboss]

36 minutes ago, Grumpy Bear said:

 

I'd say Geeks' video validated every thing I've ever said.

Guess it just needed to be said by someone else.

I'm good with that. 

 

Of course you would. 
Do you also BELIEVE that particle counts aren’t influenced by additives not heat cycled, water content adhearing to those same additives? 
Do you also BELIEVE liquid hydraulic ( oil filters) get more efficient with time? 

Edited December 21, 2025 by customboss

[Grumpy Bear]

BTW @customboss, I put you back on ignore. Not because of what you say but because I'm reactive and when I react I am no longer on task. I'm like a dog compelled to chase the squirrel which distracts me from the point I'm trying to express. Ignore allows me to hide the distraction AND see posts in order written preserving my train of thought.  

[customboss]

GM diesel 3.0 turbo diesel 

 

GM specifies SAE 0W-20 viscosity oil meeting the dexosD standard for the 3.0L Duramax (LM2 and LZ0) to optimize fuel economy, cold-start flow, and emissions system performance like DPF efficiency. Owner debates often favor thicker oils like 5W-30 based on used oil analysis (UOA) showing lower wear metals (e.g., iron ppm dropping from ~40-60 on 0W-20 to ~25-30 on 5W-30 after thousands of miles), arguing better hot protection for towing or high-heat use. No public GM test data directly compares viscosities, but the spec ties to their variable-displacement oil pump (26-41 PSI on LM2, up to 38-52 PSI on LZ0) and wet oil-pump belt design, which relies on thin oil for lubrication without a tensioner.[duramaxnews +4]

 

GM Rationale
dexosD 0W-20 prioritizes low viscosity for pump efficiency, reduced friction (boosting ~1-2 mpg highway), and belt longevity in oil (150k miles LM2, 200k LZ0). Engineering focuses on BSFC and EGTs over max wear protection, with cold-flow aiding starts in varied climates like Colorado winters.[backwoodsdiesel +4]

[customboss]

2 minutes ago, Grumpy Bear said:

BTW @customboss, I put you back on ignore. Not because of what you say but because I'm reactive and when I react I am no longer on task. I'm like a dog compelled to chase the squirrel which distracts me from the point I'm trying to express. Ignore allows me to hide the distraction AND see posts in order written preserving my train of thought.  

Understood. Do what you need to do. Keep that mental and physical health going. 
 

Im not attacking you personally. I’m challenging broad comments that have some science base but not The whole taco. 
Be well. 

[OnTheReel]

11 minutes ago, customboss said:

GM 3.0 diesel? He never says. What 3.0? European? Soot loading is NOT an issue in modern diesels. Lake mixes up gasoline engines with diesel engines. 
 

The video proves nothing about the GM 3.0 diesel using whatever vis you decide above 9 cSt @ 100c 

 

Again Grumpy and anyone that decides to run more viscous oil in your new under warranty GM 3.0 TD and show the results. 

Well, there’s only one 3.0 diesel left in production, and only one that ever called for 0w20. Not hard to read the tea leaves.

 

The FCA 3.0 spec went from 5w30 to 5w40 before they put it out to pasture. Ford 3.0 was 5w30. 

[Atlas]

1 hour ago, OnTheReel said:

At around 13:00 he addresses high viscosity oil in the 3.0 diesel and the wear reduction.

 

I must have missed where he was talking about the 3.0 specifically because I didn't catch that. He just said diesel engines dirty the oil with soot, and soot accumulation leads to more wear. All true. Soot will accumulate with whatever weight oil is chosen over the OCI.

 

The takeaway, which he gets to at the end, is changing oil more frequently keeps oil cleaner and reduces wear. I didn't read into a specific recommendation on oil viscosity for the 3.0, just that in general a higher viscosity oil reduces wear according to a chart.

 

I'm willing to give it credibility, but none of the contributors here nor in anything I've watched actually explain what a higher viscosity oil buys. Is that the difference between 200k and 400k miles or is it more like the difference between 500k and 515k miles, if the rest of the engine components happen to last that long?

 

If GM recommends 0w20 because they think it's the best intersection of efficiency and longevity and the end user stands to get 200k+ out of the engine on their prescribed oil change intervals, I think that's an acceptable life for a 1500. I'll be done with mine by 200k even if it's in perfect shape.

Edited December 21, 2025 by Atlas

[customboss]

Just now, Atlas said:

 

I must have missed where he was talking about the 3.0 specifically because I didn't catch that. He just said diesel engines dirty the oil with soot, and soot accumulation leads to more wear. All true. Soot will accumulate with whatever weight oil is chosen over the OCI.

 

The takeaway, which he gets to at the end, is changing oil more frequently keeps oil cleaner and reduces wear. I didn't read into a specific recommendation on oil viscosity for the 3.0, just that in general a higher viscosity oil reduces wear according to a chart.

 

I'm willing to give it credibility, but none of the contributors here nor in anything I've watched actually explain what a higher viscosity oil buys. Is that the difference between 200k and 400k miles or is it more like the difference between 500k and 515k miles, if the rest of the engine components happen to last that long?

It MIGHT get you 10 ppm less of iron wear with Exxon Mobil 0w20 Dexos D oil in use. 

 

Most likely mean nothing in 200,000 miles of use. 
 

Use Amsoil 0w-20 Dexos D oil and stay in grade AND have LOW iron wear. 

Maybe get you 300,000 -400,000 miles of use if maintained well. 
 

Use a too viscous oil and throw a timing belt, hold heat needlessly among others I listed above from GM design comments. 

 

[Atlas]

First OCI on my 3.0 was 508 miles. It just hit 1500 miles and it's getting changed again. when I get home. It's sitting in the garage with a battery tender on it.

 

So I guess I'm taking some of Lake's advice to heart. I have a case of ESPx2 0w20 DexosD sitting there waiting. Sounds like I should throw it out 

 

My 6.2 gasser (Camaro) hasn't gone more than 500 miles on an OCI, but that's driven more by time and not miles. 0w40 Supercar.

[Chuck FB]

3 hours ago, Atlas said:

 

Admittedly, I'm a DemonWorks skeptic. He is a tech and who also has experience with his own trucks. I have yet to see anything beyond his own anecdotal experience and providing information about the 3.0 diesel which is easily obtained.

 

I'm keeping an open mind, but the few Youtube videos I've watched I've actually become nauseous (lack of image stabilization on his cameras) and have not learned anything I did not already learn from other sources.

 

Filming and trying to work on something at the same time, I see that theme with various mechanics that are doing all the shots themselves. As to the lack of content for some aspects of an engine in real time, I know what your saying and I have gotten the impression and of no real surprise that he is not allowed to be pissing around with that at work. So I can understand your question mark based on lack of more complete content. So as to the oil analysis, its one persons sampling and lab results and so definitely others doing the same theme on the same vehicle/engine type would help give a better statistic theme to draw from for sure. 

 

One interesting item that I gather tends to be somewhat of a theme with the 3.0 and that is fuel dilution because of regens and I recall that DemonWorks truck was doing an insane amount of regens or so it seemed and he was doing various software updates that was hopefully going to improve that and it may have. Its how that engine injects its fuel into the DPF by way of using the engines fuel injectors firing into the cylinder at non firing times that I understand is the culprit to part of the fuel dilution issue. Emissions period and done in an idiotic way, like that is going to help the engine and yes who knows how much that has in itself contributed to the engine wear metals.  

[Chuck FB]

1 hour ago, Atlas said:

First OCI on my 3.0 was 508 miles. It just hit 1500 miles and it's getting changed again. when I get home. It's sitting in the garage with a battery tender on it.

 

So I guess I'm taking some of Lake's advice to heart. I have a case of ESPx2 0w20 DexosD sitting there waiting. Sounds like I should throw it out 

 

My 6.2 gasser (Camaro) hasn't gone more than 500 miles on an OCI, but that's driven more by time and not miles. 0w40 Supercar.

 

While its not like I have any personal data to draw on other than what I come across online, I too have wondered with my L8T, what is the most logical approach to the engines health AND at the same time maintaining my wonderful GM warranty. While it may fly in the states to use oils that are said to meet a certain spec ( Dexos 1 Gen 3, or its the DexosD in your case ) , if it doesn't carry the actual license it becomes an issue here in Canada from how the dealer is telling me. 

 

So my view point based off of the picture I am faced with here, is that if I had a 3.0 I would more than likely initially stick with the DexosD licensed 0W-20 and change it plenty often and certainly during the break in stages as it sure can't hurt anything. Because of the soot factor and the potential for the fuel dilution the 3.0 seems to have issues with, that also helps reinforce the concept of no matter what oil is used, get that soot and diesel diluted oil out of there by changing it a lot more often then the oil change minder would call for. Unfortunately no matter how much one would spend on a high end oil of the same viscosity as GM calls for, it can't help but get contaminated with soot and raw diesel fuel. If the unit was deleted, yes that would take care of a lot of the soot contamination issues and the diesel dilution ... and wave bye bye to your warranty. They got us all by the balls no matter what brand of vehicle one buys !.