Mystery Oil Loss - Where is the oil going? 2008 Yukon Denali

[Gildan]

This one is baffling. I mean, truly baffling.

The issue: Intermittent oil loss of at least one quart of oil. I had the oil uptake O ring and oil pump on my Denali for the usual reasons. Now the problem is even worse and has become absolutely bizarre.

OK, so if I drive 1000 miles at highway speeds I don't lose a drop of oil, but it I drive locally, I'll lose a quart in 100 mile, but it occurs at random. I check the oil in the morning and evening to verify this all. I get up in the morning, the oil is at the full mark. I drive less than 50 to 100 miles locally, go home in the evening and the oil is exactly full. The next morning I check the oil and a quart has vanished. There is no oil on the ground in the garage, and absolutely no sign of a leak anywhere. But, sitting over night, a quart of oil has vanished. This will happen every two days just like clockwork. Every two days. Sometimes a quart of oil will vanish in a 20 mile trip, no smoke, no leaks, no nothing).

There is no smoke from the tailpipe at all at any load or speed (I had someone follow me to verify, and they observed no smoke at all even when a quart vanishes in a 20 mile trip, which is another issue). We checked all the seals, no leaks; We checked the compression, and it's exactly factory specs. The spark plugs have absolutely no deposits on them whatsoever. No oil contamination of coolant and vice versa. Where is the oil going and why?

I even hung a sheet under the chassis and drove and not a speck of oil, yet a quart vanished in as little as 10 miles. And this occurs at two day intervals like clockwork. I can check the oil and not drive the vehicle for two days and at two days, a quart vanishes with not a drop on the ground. I even checked the catch can on the snorkel and not a drip. The oil just vanishes even while parked.

There are no performance issues. I get 23-28 mpg in the highway and 17 local; I get 15 mpg pulling a loaded two horse trailer local or highway. The oil loss always seems to occur when I am parked overnight and nearly only when I am parked over night. But never a speck of oil under the vehicle. I even sent the oil off for analysis and there is no dilution or significant contamination other than what would be normal - however, I had the mechanic who did the O ring and oil pump check everything and he is totally puzzled; I had a stealership check it out and they are puzzled and said they've never seen anything like it before. The only common conclusion is that the oil companies are selling Zero weight oil and labeling it 5W-30 and it's degrading and evaporation. No one can explain it.

Any thoughts on this one? Has anyone seen this type of thing before?

 

[petethepug]

My 08 YXL Denali did that too. Had it from 96k to 140k over six years til 2020.

Does someone have the part # of the updated valve cover handy?

 

[swathdiver]

2007-2008 used 12582224

I had a GM 3900 that every couple of years would suddenly consume all of its oil. I could only surmise that all of the gaps on the piston rings had lined up allowing the oil to more easily pass into the combustion chamber.

My truck uses oil prodigiously when my wife and daughters drive it. The routinely spin the motor up over 3500 rpms. I rarely turn it that much when driving.

 

[Gildan]

I thought about that updated valve cover issue and I'm going to look into it.

 

[rdezs]

I'm a firm believer in looking at the easiest and frequently the obvious cause. Take a flashlight and make sure your dipstick tube isn't rusted through just below the exhaust manifold..... And intermittently your dipstick sliding through the rust hole. Just throwing that out there

 

[rdezs]

.... Thinking outside the box here.... Have we looked at your coolant? You're not pumping oil into your cooling system through a crack in the oil cooler? I would think you would have noticed that by now.... Just a wild thought.
I'd be putting a PCV catch can on it right away and monitoring it.

 

[Gildan]

2007-2008 used 12582224

I had a GM 3900 that every couple of years would suddenly consume all of its oil. I could only surmise that all of the gaps on the piston rings had lined up allowing the oil to more easily pass into the combustion chamber.

My truck uses oil prodigiously when my wife and daughters drive it. The routinely spin the motor up over 3500 rpms. I rarely turn it that much when driving.

Funny you should mention the RPM issue. I was talking to a friend in Tennessee who said that his '08 Puke started doing this after the first time he used the 'trailer/tow' feature to pull a trailer and never quit after that until he literally flooded a solvent (he used MAF sensor cleaner) into the tube and let it sit for an hour or so and cranked up the motor.

The trailering/tow mode on these vehicles absolutely sucks. The reason is that you don't shift out of 1st or 2nd gear unless you hit 3000 RPMs or better. That, and when you are cruising on a flat surface at 55mph, it keeps flipping back and forth from 4th to 5th at 2000-2500 RPM. It overruns the motor unnecessarily.

The second possible issue is a faulty oil pressure sensor sending bogus data to the ECM but he isn't quite sure why this would be (I do have to say that my OEM GM oil sensors bought directly from the dealership fail after about 3 or 4 months. I've gone through about 4 per years that have failed, and they are a dog to replace unless you remove the intake manifold to get to it. Otherwise, you'd better be an acrobat and contortionist to replace the sensor without removing the manifold).

The gaps in the rings is a distinct possibility for the intermittent nature of the problem. I stuck a bore scope camera into each cylinder to look for scoring or other defects and found nothing and the compression is as good as new. But that's possibly part of the problem. The one issue is that GM put the wrong O rings in the oil uptake tube in at the factory just to meet production demands and the second issue contributing to it was that they didn't install the deflector on the return tube of the oil cooler (which means that the oil sprays right up into the crank shaft and will sludge up your motor in a New York minute and sludge up your PCV orifice).

I haven't decided whether or not the GM design engineer are incompetent or malicious.

"Incompetence carried to a sufficiently advanced level is absolutely indistinguishable from deliberate malice." - Gray's Law

 

[Gildan]

.... Thinking outside the box here.... Have we looked at your coolant? You're not pumping oil into your cooling system through a crack in the oil cooler? I would think you would have noticed that by now.... Just a wild thought.
I'd be putting a PCV catch can on it right away and monitoring it.

I thought of that exact possibility. The plastic gallery for the intake has a catch can, but it's dry as a whistle, but that's not the only path oil can be sucked up into the intake manifold and leave no oil in the catch can. There is an after market catch can you can add if you don't already have on. It essentially plugs the intake manifold receptacle and runs the PCV into a can, so to speak. The motor will run better, you don't lose oil, per se, by the tree huggers will go berserk. You'd think if you were burning a quart of oil in 20 to 100 miles you'd have a smoke screen behind you.

The oil cooler on this vehicle is a separate affair and not in any way connected to the radiator as is the same for the transmission cooler, so it would be unlikely to get oil and coolant transfer unless a head gasket is blown or there is a crack in the blocks which isn't the case here. I have a separate oil cooler, etc., and there isn't any milkshake or moisture on the oil filler cap or in the antifreeze (and the compression is perfect).

I usually shoot for the simplest and cheapest possibility before I go down the rabbit hole with GMC. LOL

 

[B-train]

This one is baffling. I mean, truly baffling.

The issue: Intermittent oil loss of at least one quart of oil. I had the oil uptake O ring and oil pump on my Denali for the usual reasons. Now the problem is even worse and has become absolutely bizarre.

OK, so if I drive 1000 miles at highway speeds I don't lose a drop of oil, but it I drive locally, I'll lose a quart in 100 mile, but it occurs at random. I check the oil in the morning and evening to verify this all. I get up in the morning, the oil is at the full mark. I drive less than 50 to 100 miles locally, go home in the evening and the oil is exactly full. The next morning I check the oil and a quart has vanished. There is no oil on the ground in the garage, and absolutely no sign of a leak anywhere. But, sitting over night, a quart of oil has vanished. This will happen every two days just like clockwork. Every two days. Sometimes a quart of oil will vanish in a 20 mile trip, no smoke, no leaks, no nothing).

There is no smoke from the tailpipe at all at any load or speed (I had someone follow me to verify, and they observed no smoke at all even when a quart vanishes in a 20 mile trip, which is another issue). We checked all the seals, no leaks; We checked the compression, and it's exactly factory specs. The spark plugs have absolutely no deposits on them whatsoever. No oil contamination of coolant and vice versa. Where is the oil going and why?

I even hung a sheet under the chassis and drove and not a speck of oil, yet a quart vanished in as little as 10 miles. And this occurs at two day intervals like clockwork. I can check the oil and not drive the vehicle for two days and at two days, a quart vanishes with not a drop on the ground. I even checked the catch can on the snorkel and not a drip. The oil just vanishes even while parked.

There are no performance issues. I get 23-28 mpg in the highway and 17 local; I get 15 mpg pulling a loaded two horse trailer local or highway. The oil loss always seems to occur when I am parked overnight and nearly only when I am parked over night. But never a speck of oil under the vehicle. I even sent the oil off for analysis and there is no dilution or significant contamination other than what would be normal - however, I had the mechanic who did the O ring and oil pump check everything and he is totally puzzled; I had a stealership check it out and they are puzzled and said they've never seen anything like it before. The only common conclusion is that the oil companies are selling Zero weight oil and labeling it 5W-30 and it's degrading and evaporation. No one can explain it.

Any thoughts on this one? Has anyone seen this type of thing before?

That is absolutely bananas......but props on the excellent MPG score!

 

[j91z28d1]

so details on this oil. are you filling it back up every time you find it a qt low?

what if you don't fill it, will it come back up after a day of driving and be lower again in the morning? Other members have filled the kids can full and very short mileage until they replace the valve cover and soak the Rings. Around town actually makes sense to use more oil because vacuum through the PVC system is much higher under decell than it is just cruising down the highway


first thing, change that valve cover. it fixes almost everyone's oil use and I might be reading your post wrong but I'm not sure you understand a catch can fully. you don't block anything off to add it and you definitely don't have one stock in the intake. tree huggers do not care if you have a catch can lol. nothing is vented.

 

[Gildan]

so details on this oil. are you filling it back up every time you find it a qt low?

what if you don't fill it, will it come back up after a day of driving and be lower again in the morning? Other members have filled the kids can full and very short mileage until they replace the valve cover and soak the Rings. Around town actually makes sense to use more oil because vacuum through the PVC system is much higher under decell than it is just cruising down the highway


first thing, change that valve cover. it fixes almost everyone's oil use and I might be reading your post wrong but I'm not sure you understand a catch can fully. you don't block anything off to add it and you definitely don't have one stock in the intake. tree huggers do not care if you have a catch can lol. nothing is vented.

Interesting points. The oil level drops over night by a quart while the vehicle is sitting. Let me do a deeper dive into the phenomenon.

I drove from North Carolina to my new house in Arkansas while pulling a trailer using the trailer/tow mode as per the owner's manual. This alone would normally result in a bit of oil consumption due to the increased RPMs overall and especially due to the automatic downshifting on inclines and for engine breaking (This, under normal conditions could account for oil consumption for a number of reasons). Over 650 miles of the total distance, I didn't lose a drop of oil. I parked the vehicle, waited half an hour and checked the oil level (I check the oil level every time I stop for fuel anyway) and the oil level was spot on to the full line. In the morning I checked it again and low and behold, it was a quart low. There was no oil under the vehicle nor any on the undercarriage to be found, yet a quart vanished.

I topped the oil off to the full line, drove the vehicle about 30 miles (with the trailer), parked it again at the house, checked the oil and it was spot on full. The next morning it was yet again a quart low. Topped it again and drove about 30 miles on my way back to North Carolina, checked the oil and it was fine. I stopped for lunch, came out and checked it again before setting out and SOB, it was a quart low with no oil on the ground or leaks to be found. I topped the oil, drove the last 600 miles and arrived in North Carolina, checked the oil level and it didn't lose a drop. Drove around for two days (about 100 miles) with no oil loss. Parked the car on the second day in the garage in NC, checked the oil in the morning and SOB, it was a quart low in the morning without any oil under the vehicle or any detectable leaks. A quart of oil simply vanished without any trace or cause while sitting in the garage over night. Topped it in the morning, and two days later checking the oil twice par day, a quart vanished over night while parked. Then another two days without an issue and BAM, a quart vanished over night while the vehicle was sitting, again without any puddles under the vehicle or any signs of a leak anywhere (I used a florescent dye in the oil just to make sure there was no leaks and there were no leaks).

That said, on the big plastic intake snorkel there is a what is tantamount to a catch can near the Helmholtz resonator, but it is dry as a bone.

Just an a diagnostic wild arse guess test about an hour ago, I tried an interesting experiment involving the PCV method used on this particular 6.2L (which has a tube with an orifice on it for the PCV but no PCV valve, per se). I pulled the valve cover with the integral PCV orifice and flushed it out with a proper solvent, replaced the valve cover with a new gasket and something very odd happened - my oil pressure went up by abut 5 to 10 PSI all around. I parked the Puke in the garage and checked the oil level after the oil settled for half an hour and it was spot on full. An hour later, a quart was suddenly gone with no oil on the ground and no leaks whatsoever. The oil seems to vanish while the vehicle is sitting still in the garage. And no one can figure it out because unless there's a glitch in the matrix, the oil is simply vanishing into a black hole (and this was after a 20 mile trip for test purposes). If I was losing a quart of oil out the tailpipe in 20 miles I'd have a cloud of blue smoke behind me that would be visible from outer space.

Unless there is something severely odd about the vapor pressure characteristics of the oil or the laws of physics, there is absolutely no explanation of why this is happening.

 

[swathdiver]

I think your rat found his way into my garage. My daughter grabbed a bottle of oil off the shelf the other day and oil spilled all over her leg and onto the floor. The cap was tight, when she turned the bottle around, we could see where a rat had eaten through the 1 gallon bottle exposing the oil. Or maybe there's two of them!

My transmissions are also in front of 3.42s and don't hunt for gears while towing. Tow/Haul provides no benefit unless your GCW is over 10,500 pounds.

 

[rdezs]

A couple noteworthy points.....

1. Your fuel mileage, while much better than average, could be a symptom. Such as.... You have additional fuel entering the cylinder. Oil. Theoretically, if it's entering as a mist, it is possible it's burning fairly clean..... But that clearly doesn't address oil disappearing overnight. And if it is going out the tailpipe, most people would be in agreement that your catalytic converters are not long for this world. But let's not forget there's many diesel pickups out there with catalytic converters..... I have a Ford 6.0 powerstroke that came with one.

2. Time to get an oil analysis done. It might be useful to see what actually is in your crankcase.

3. If your oil is extremely aerated, and full of air bubbles... And sits overnight.... Yes, the oil level will drop much like a glass of beer with foam on top. But... I would expect your oil level, for example after driving in town for an hour, to be a quart high on the dipstick.

4. At this point I would dump the oil and filter and take a sample after a brisk 20 minute drive around town. Catch some in a glass jar and take a close look at it for trapped air bubbles. Mark a line with a sharpie at the oil level in the glass jar and let it sit overnight. While awaiting the oil sample results, I'd put some 10W-40 in and see if the symptoms change.

5. Oil aeration is not uncommon in LS engines. Besides oil being whipped up around the windage tray, the oil being released from the pumps pressure relief valve becomes very aerated. Anti foaming additives in motor oil are supposed to address this. So as a test of sorts, I would switch to something like the Valvoline synthetic high mileage motor oil. (Which raises the question, exactly what oil is in the pan and what oil are you adding?) And yes, extremely aerated oil will create more vapor in the engine and be sucked through the PCV system to be burned.

My best speculation is the root cause may in fact be the oil pump itself, possibly in conjunction with the oil you are using and it's inability to control foaming. You also mentioned the mechanic change the o-ring on the pickup tube. If he used the wrong o-ring, the smaller one or got it in there wrong, sucking a little bit of air and will also aerate it inside the pump.

That's about all I can think about on this.....

 

[B-train]

This is good information.

After reading through all this, here's my thoughts.

1. Checking hot will have a higher level as all things expand when hot. This would explain why it appears lower when it cools off.
2. @rdezs has a good speculation on the oil getting whipped up. Is it possible that you keep adding an extra quart that gets whipped up and consumed due to being overfull?
3. I'd drain the oil when hot. Refill with 6 quarts of 5w-30 and a new filter of the correct size. Your level should be spot on the Full mark.
4. If it changes overnight, then you must have an oil gremlin.....

 

[donjetman]

@Gildan
GM TSB 10-06-01-008M
https://www.tsbsearch.com/GMC/10-06-01-008M
includes:
driver side valve cover GM# 12570427, same as Dorman# 264-965
pressure relief valve deflector GM# 12639759
piston/combustion chamber soak

Prior to doing this TSB, many of us have installed a catch can to verify the oil was being sucked out thru that path:
https://www.tahoeyukonforum.com/threads/get-a-catch-can-before-any-mods.49716/page-53#post-1288561

Hundreds of folks at this forum have had this problem, myself included

 

[j91z28d1]

just to add while the air intake is technically part of the pvc system. but It's not the part where you usually see oil. you'd basically have to be doing track days or have a cracked ring land to blow oil back up the clean side air intake. the oil gets sucked in to burn from the drivers side valve cover. hince the updated part number with working oil baffles in it


I feel rdezs is on to something with the foaming oil, you're using what is a fairly normal amount of oil for that old style valve cover but it's not showing up on you dip stick till it sits long enough.

that's all that makes sense short of a glitch in The Matrix.


what is you oil pressure out of curiosity?

 

[Fless]

That said, on the big plastic intake snorkel there is a what is tantamount to a catch can near the Helmholtz resonator, but it is dry as a bone.

What does this catch can looking thing look like?; post a pic of it.

Any chance you took a pic of the underside of the driver's side valve cover when you had it off? If so, please share.

 

[jeffluan]

Don't know if this vehicle has a PCV valve but I have a friend who using oil in a non GM vehicle. It appears as of now the problem is solved with that car. I would start there. If you shake it and there's no rattle, replace it and see.

 

[Charlie207]

What does this catch can looking thing look like?; post a pic of it.

Any chance you took a pic of the underside of the driver's side valve cover when you had it off? If so, please share.

It's just a dingleball that hangs down on the intake... another frequency tamer.

 

[j91z28d1]

Don't know if this vehicle has a PCV valve but I have a friend who using oil in a non GM vehicle. It appears as of now the problem is solved with that car. I would start there. If you shake it and there's no rattle, replace it and see.

no pvc valve. these run full bore