Crank Case Ventilation (CCV) the source of oil consumption in the GM 3.0L Duramax?

[wwillson]

I documented in this thread that my Chevy 3.0L Duramax uses about 1 quart of oil in 10k miles.

https://bobistheoilguy.com/forums/t...les-278-total-hours-hpl-0w-20-dexos-d.387862/

@High Performance Lubricants was gracious enough to blend a Dexos D 5w-30 with a low volatility to attempt to reduce oil consumption. I now have 8k miles on the HPL 5w-30 and it appears that the oil consumption will be right at 1 quart at 10k miles. This lead me to look for other causes of oil consumption, because it doesn't make sense that the consumption would be the same if volatility was the cause.

Lots of internet reading lead me to suspect oil could be passing the CCV and be ingested by the engine. The CCV system vents into the intake side of the turbo. If the oil loss is through the CCV, then the intake system past the turbo should have oil residue. I pulled the hose between the turbo output and the intercooler so I could get some pictures of the inside of the intercooler with my bore scope.

This is what I found:

Engine oil and quite a bit of it. I have no way of knowing how much engine oil gets sucked into the turbo from the CCV over 10k miles, but it's more than none.

My search lead me to this well engineered catch can for the LM2/LZ0.

https://runvse.com/2020-2025-vse-lm2-lz0-ccv-catch-can-suv-and-pickups/

There is a video on their youtube channel that shows the oil what was caught on a 1,000 mile trip. It was about 3 oz, which is about 1/10th of a quart. Well isn't that interesting.

I'm going to install the catch can and document how much oil I pour out over 10k miles.

This is going to be interesting.

 

[JHZR2]

Is there an oil separator before the turbo? Some of my turbo diesels have a cyclonic separator and drain so the vapors go into the turbo intake, the oil drains to the sump.

 

[wwillson]

Is there an oil separator before the turbo? Some of my turbo diesels have a cyclonic separator and drain so the vapors go into the turbo intake, the oil drains to the sump.

Nothing visible. There could be something under the valve cover, but it clearly isn't doing a good job.

 

[Number_35]

Near the end, the tired old 307 in my '68 Impala consumed oil at approximately 120x the rate of your Duramax.

I swapped in a slightly less tired 327 from a '69 BelAir, and oil consumption plummeted to 50x that of your engine.

Don't do the math - it's too cringeworthy.

I would have been thrilled with a quart every thousand miles.

 

[SubieRubyRoo]

Near the end, the tired old 307 in my '68 Impala consumed oil at approximately 120x the rate of your Duramax.

I swapped in a slightly less tired 327 from a '69 BelAir, and oil consumption plummeted to 50x that of your engine.

Don't do the math - it's too cringeworthy.

I would have been thrilled with a quart every thousand miles.

Your 307 burned 3 gallons of oil every 1k miles?

 

[Number_35]

Your 307 burned 3 gallons of oil every 1k miles?

It went through a quart every 75 miles. On the last major road trip, I had an extra set of plugs. I had to swap every few hundred miles.

 

[CleverUserName]

If your up to making a bracket and running hoses, the Mann pro-vent does it all and better while providing:

• Oil vapor seperation
• Over pressurization protection
• Provisions to return oil to sump.

 

[tnt_motorsports]

that is crazy @wwillson! Do you know if you have blowby issues? Not likely given the vehicle is somewhat new, but it might be worth a check. On my Cummins you take the oil fill cap off the valve cover and turn it upside down and watch it dance. My Cummins hardly moves at 120K miles. I also don't have consumption issues like you described. have you let GM know about this? It seems excessive to me.

Another thought might be to change your CCV filter. I know on the Cummins if they are saturated it can increase the consumption.

Just my $0.02

 

[wwillson]

Do you know if you have blowby issues? Not likely given the vehicle is somewhat new, but it might be worth a check.

My assumption is no. The engine has ~600 hours so there should be almost zero wear.

have you let GM know about this?

No, oil consumption in the 3.0L is universal. They run the oil very hot, which certainly contributes to oil venting through the CCV.

Another thought might be to change your CCV filter.

I believe it's integrated with the valve cover, so replacing isn't feasible and these engines consume oil from the beginning. There likely is no "filter", but a separator that doesn't work all that well.

 

[cptbarkey]

25 year older technology, but the CCV on my 5.9 has a charcoal type filter where one tube routes back into the block (not the turbo) and another tube pukes it to the ground. Goofball but it is what it is.

 

[johnmyster]

No, oil consumption in the 3.0L is universal. They run the oil very hot, which certainly contributes to oil venting through the CCV.

I hadn't realized they ran those engines so hot. Apparently, nominal ECT is around 220 F and it makes sense that oil temperature would run some level above that based on some balance between piston cooling (source) and oil cooler (sink).

I wonder if any of the reputable aftermarket tuners (CPS, PPEI, etc) have experimented with bringing this down (for some reason) with a lower temp thermostat and "corrected" tuning.

I realize there is a secondary cooling system (like the 6.7 powerstrokes and L5p?) for charge air cooler, trans cooler (?), fuel cooler (?) etc.


Ram 6.7 and Powerstroke 6.7 both use a CCV filter as a catch can, of sorts. There's a filter element that, when saturated, drains back into the crank case and/or valve cover. Idea is to remove oil mist from CCV exhaust to prevent oil consumption and internal lubrication of the intake tract. To some degree, it works. Some oil still coats the intake system innards. On the Fords the housing and lines crack or become disconnected and leak oil all down the side of the engine. Neglect (running the CCV filter too long) is associated with increased crankcase pressure and oil leaks from various engine seals, many of which are a bear to replace.

25 year older technology, but the CCV on my 5.9 has a charcoal type filter where one tube routes back into the block (not the turbo) and another tube pukes it to the ground. Goofball but it is what it is.

The first duramax engines (LB7, federal emissions configuration) were this way too. It's a catch can of sorts where the oil drains back to the crankcase and the blowby gasses are vented to atmosphere with any oil carryover. My LBZ, which was allegedly emissions intact may or may not have had the CCV routed to the ground. I never noticed any oil residue discharge from the hose, even towing, that allegedly might have existed, despite a certain degree of blowby after 300k miles.

I don't recall how much OP says he tows but I would expect increased load on the engine to correspond to increased natural blowby and increased oil consumption.

 

[OneLonelyBurrito]

In GM paper about the LM2, they claim the CCV system is 98% efficient at removing oil from the blow-by. They claim in normal driving the amount of oil getting consumed through the CCV system is less than 1.5g/hr. If my conversion is correct, 1.5g/hr equals ~2ml/hr of motor oil. So over say, a 250hr oil change interval, that would be 500ml or about 0.5 quarts. I can't say what they mean by "normal" driving, but it does seem like a lot of oil to be going through the CCV system

 

[wwillson]

I realize there is a secondary cooling system (like the 6.7 powerstrokes and L5p?) for charge air cooler, trans cooler (?), fuel cooler (?) etc.

6.6L Duramax has a separate liquid fuel cooling system, but the charge air is air-to-air.

3.0L Duramax has a separate liquid charge air cooling system, but no separate fuel cooling system that I know of.

 

[johnmyster]

6.6L Duramax has a separate liquid fuel cooling system, but the charge air is air-to-air.

3.0L Duramax has a separate liquid charge air cooling system, but no separate fuel cooling system that I know of.

Yes. I realized the functions of the secondary were unique for each platform, attempted to note it as such. I knew the 3.0 had a air-liquid charge air cooling system on a secondary coolant system, but didn't realize what other functions it might serve. Diagrams are not out there for it.

The 6.7 powerstroke is a plumbing nightmare. Six thermostats. Brittle hose fittings and pipes everywhere.

 

[wwillson]

In GM paper about the LM2, they claim the CCV system is 98% efficient at removing oil from the blow-by. They claim in normal driving the amount of oil getting consumed through the CCV system is less than 1.5g/hr. If my conversion is correct, 1.5g/hr equals ~2ml/hr of motor oil. So over say, a 250hr oil change interval, that would be 500ml or about 0.5 quarts. I can't say what they mean by "normal" driving, but it does seem like a lot of oil to be going through the CCV system

"Normal Driving" I can imagine that means mostly in-town driving. Most of my driving is 75 MPH cruising down the interstate, which gets the oil a lot hotter and keeps it whipped up likely producing more oil mist.

 

[BrianF]

Very interesting post and hope to follow your journey on this.

I ran into a similar issue on my 2017 Ram 6.7 Cummins. The factory fill 5w40 and subsequent 10w30 (conventional and semi synthetic) fills showed no discernable oil consumption, ran one 24,000km index with a semi synthetic 5w30 and came up with 1 litre of consumption around the 18k mark. Switching back to 10w30 reverted back to no discernable consumption.

The 6.7 has a replaceable CCV filter, which I believe works for the most part but there has always been some amount of oil that gets by. I remive my intake ducting to change the oil filter and inspect the turbo each change. I have yet to scope the intercooler and see what sort of mess waits.

 

[Jetronic]

if that oil you're using has high solvency, it should help prevent intake coking up.

 

[OneLonelyBurrito]

"Normal Driving" I can imagine that means mostly in-town driving. Most of my driving is 75 MPH cruising down the interstate, which gets the oil a lot hotter and keeps it whipped up likely producing more oil mist.

Yeah I'm assuming they are using the the FTP75 & HWY drive cycle as their "normal driving", since those are much lower RPM and Load than the US06 "aggressive" drive cycle.

 

[tnt_motorsports]

25 year older technology, but the CCV on my 5.9 has a charcoal type filter where one tube routes back into the block (not the turbo) and another tube pukes it to the ground. Goofball but it is what it is.

yeah, this all changed with emissions, no more slobber hoses... My 2012 Cummins Ram, which is before Tier 4, so non-DEF, has a DPF and a CCV.

Just my $0.02

 

[tnt_motorsports]

My assumption is no. The engine has ~600 hours so there should be almost zero wear.


No, oil consumption in the 3.0L is universal. They run the oil very hot, which certainly contributes to oil venting through the CCV.


I believe it's integrated with the valve cover, so replacing isn't feasible and these engines consume oil from the beginning. There likely is no "filter", but a separator that doesn't work all that well.

thanks @wwillson, this would not make me happy. Once the system is contaminated with oil it is a real mess!

Just my $0.02