All of the sudden...I'm burning oil?

Hey all, I'm hoping the hive mind can help me understand why my 2013 base 4-cyl manual (~190K mil) is suddenly burning oil.

I recently paid to have a cracked head gasket serviced, which included getting the head re-surfaced. Now it burns oil. And not just a little. The mechanic did a fresh oil change and when I came back after 3K miles, he said it's burning about 1 quart every 1K miles.

When I asked him "why now?" he said that that it's likely because I wasn't getting enough pressure in the cylinders (due to cracked gasket), that it wasn't as bad and thus not noticeable. Now that I do have full pressure, it's noticeable (both by smell and by measurable volume). Either way, he says, the problem was always the same: aging o-rings [EDIT: piston rings, not o-rings].

Does that sound right? It makes sense, but I wanted to know if there's anything else to look at since this basically means this engine is in its end year(s) and I may soon need to decide if I should replace it or buy a newer vehicle altogether.

 

Aging o rings? If you got that correct, time for a new mechanic.

Maybe valve stem seals, but that should have been an easy fix with the head off, especially if it was machined.

Something's not adding up here......

 

BS answer.

Ultimately, unless you have proof, like valve seals or ring lands, its guessing.

It's likely gummed up ring lands, which is related to PCV and the nature of the 4 banger. They recirculate the engine gasses and it accumulates on the pistons eventually causing blow by. This is usually the case, but a guess.

Valve seals can cause this too, but usually its not even anywhere close to that consumption, and most report smoke puffs before oil use. Plus they should have been replaced during the headgasket repairs.

 

depends what “mechanic”.

not sure what you mean by O-rings. Tail light connector O-ring?

piston rings can be worn. There’s tests for this.
Odd coincidence for it to start at the same time. Usually caused by long term neglect, gradual, noticeable, doesn’t go away.

conpression test, wet and dry
Leakdown test
There’s also degunking products and services

inspecting tailpipe; it’ll be black on a vehicle that’s been burning oil for a while also killing cat(s) causing P0420, and smoking/smell if extreme

oil choice is a factor. Or failed PCV system.

head worked on by a good machine shop will have quality valve stem seals properly installed. Any issue with valve stem seals will burn oil.

1qt/1000 happens on carboned rings or installed upside down
carboned more of a thing on spring type rings instead of better waffle type. Not sure what 2TRFE comes with.

leaking valve stem seals you can probably see oil puddle inside with borescope.

 

It used no oil prior to the repair?
A cylinder leakage test might help tell you where it’s going. Did your mechanic only replace the head gasket or did he do some head work as well?
If he did valve work he probably screwed up the guides or stem seals.

 

it is NOT from the regained pressure; that shows the mechanics lack of knowledge. The are no orings involved that can send oil to a cyl to be burned. Unless the mechanic pulled pistons for some strange reason, the most likely scenario given the work done and symptoms (no oil burn, redo heads and burns like crazy) was that the head shop left off one of the stem seals or installated it incorrectly. Many need adhesive to hold them on and lazy mechanics sometimes don’t clean the oil off and therefore adhesive fails. He could also have left the old ones in place and ripped one when installing the valves. These are not your grandfathers umbrella seals. The head design leaves a small pool of oil near each lifter. I believe this is the reason our mechanical lifters never wear and need adjustment. Therefore a compromised stem seal will create a good size oil consumption rate. Let the engine idle for 5 minutes, shut down and pull plugs. The culprit cylinder should have oilly wet plugs. At higher rpms the plugs get hot enough to burn the oil off them, but idle doesn’t generate enough heat to do that. Unfortunately, replacing stem seals means pulling the cams and the valve springs. Not a terrible job, but not really for a novice. If you have a borescope, you can probably see which valve is the source.

issues with rings or cyl walls makes no sense given the sudden onset after only head work.

 

Thank you everyone for the insights and education. I corrected the original post. My use of "o-rings" was me being dumb and under-caffeinated. I meant piston rings. Sorry for the confusion.

@TacoTuesday1 I checked my tailpipe and it was not black. Thanks for the suggestion.

From what I've learned from you all, I'm going to try the following (in order) and report back:

1. Idle test as suggested by @lr172
2. If oil on a plug, request use of borescope to identify valves in need of adjustment and get those done. If still an issue...
3. Compression and leak-down test as suggested by @TacoTuesday1 and @Rusty66
4. Troubleshoot PCV as suggested by @Bishop84 and @TacoTuesday1

@Rusty66 I checked the paperwork to see if any head work was done in addition to the resurfacing. Here is what was listed on the work invoice:

1. Cylinder head gasket - remove and replace - includes R&I engine assembly. Remove carbon and check surfaces for warpage. Includes adjust valves (where applicable) and clear and adjust spark plugs.
2. Head milling​

I learned a lot from everyone. Truly appreciated.

 

Following up on this. We checked the plugs and they were clean. Compression tests looking good. I did not check the PVC, but have come to believe the mechanic's conclusion: that the engine is burning oil due to worn oil rings on the pistons. We weren't seeing it before because the compression was low due to a cracked head gasket. The crack was small and we didn't notice it until it finally became big enough to be obvious. Replacing it meant we had full compression, and thus more oil burning. He said it's not a big deal and that it does not affect the life of my engine. Just keep pouring oil into it as needed between oil changes.

 

You may need to find a different mechanic. A lot of this does not make any sense. Engines with good compression usually have functional piston rings.

 

More bad data from the mechanic. It is true that a bad head gasket will reduce compression, but only on the cyl(s) affected by the blown HG (rarely all of them). It is true that once the HG is replaced that compression will come back up, but this only increases blow by, not oil consumption. Each piston has two compression rings and one oil control ring. Loss of cross hatch on the cyl walls and/or failed oil rings are what cause oil consumption and neither are related to the compression achieved. Excessive blowby can cause a minor amount of oil loss via the PCV circuit, but would not be significant. leaky compression rings will NOT cause one to burn 1 qt in 1K miles.

When piston goes up, the rotating crank splashes oil on hte cyl walls. As the piston travels down, the oil ring scrapes off most of it, leaving only oil in the cross hatch crevices. When you have issues with the walls or the oil ring, it leaves too much oil on the walls and it burns off during the next power stroke and this is how you get oil loss. None of this has anything to do with compression levels.

If you went 5K miles between oil changes without losing much oil and now burn 1 qt in 1K miles, they must have done something wrong while replacing the HG's. That simply can't be attributed to regained compression in two cylinders.

 

What are your compression numbers, suspiciously high compression in an old engine can also mean the rings are bypassing too much oil... just for fun if you have the time and a warm place, spin the engine by hand with the plugs out until you get one all the way down. Look in with a borescope and look at the cylinder walls all the way around. It should have crosshatching and not a mirror shinned surface on the cylinder wall in a spot or two. Cylinders 1-4 and 2-3 are running mates so which ever is all the way down you can check it's buddy at the same time before spinning it over again.

A section on the cylinder wall with a shinny spot and no crosshatching is game over for the block.

If you have cross hatching all the way around or just want to try something anyways, get some acdelco top engine cleaner(comes in a 1 litre can) and pour some down each cylinder. Just enough to cover the piston tops. After that spin the engine around a few times by hand then park everything about midway and take note of the fluid level in each cylinder.
After an hour look again. They should all be at the same level you left them at. If one significantly drops then those are the rings that are seized.

Dump more top engine cleaner in that cylinder and periodically check them all. I've had good luck freeing stuck rings like that, however if your cylinder walls are worn then it will be better but still always burn some oil because of the cylinder walls.

After your "piston soak" you'll have to change the oil since the chemicals will be in the oil and they are very aggressive so don't run the engine with it in there. After the oil change, leave the plugs out and crank the engine with your foot firmly to the floor on the gas pedal or otherwise disable the fuel injectors to clear the cylinders. Add a little oil to each cylinder after that then crank again with the plugs out. Thats important to do because the chemical will strip all the oil from the cylinders and pistons and without the little oil it may struggle to start because it's trying to build compression dry.

 

Cleverly spoken, not the life of the engine, just the emissions system.
Next invoice: New Catalytic converter, clean and replace O2 sensors, white glove test - clean residue from muffler, rebuild muffler bearings.

But in all seriousness, if you burn enough oil then eventually the catalytic converter won't work efficiently enough to clean the exhaust you'll wind up with the P0420 code as TacoTuesday mentioned. CAT's aren't cheap.