Burning oil

[Blkwolf87]

Hi guys,

I’m new to forums but not new to subaru. I work with my father who owns an independent Subaru repair business. I’ve got a 2005 Subaru Legacy outback with a 2.5 four cylinder non-turbo SOC. We’ve both spent some time on my car trying to figure out why it’s burning through oil. I’ve recently done HG, pistons/rings, valve stem seals/cover gaskets, oil pickup tube ring, and cleaned the pcv valve which was pretty dirty in my opinion. I did the pistons and rings because I did a compression test and found that cylinder 3 was a lot lower than the others. Also had the valves cleaned and resurfaced when the stem seals were replaced. Found oil in cylinder 3 on top of the piston and had build up on the valves for that cylinder. The only other things I can think of is maybe the rings on the dipstick tube are worn and sucking air through that, maybe a warped cylinder, or possibly the pcv passage is kunked up not allowing proper ventilation through the pcv valve. I got to fill it back up every week to two weeks depending on how much I gotta drive. Why is it still burning oil? I notice grey to white smoke out the back when getting onto the freeway. No noticeable smoke in city or at idle. I don’t know what else to do?

 

[Blkwolf87]

Also want to note that we also own a 2006 legacy sedan that has no issues when it comes to oil loss or burning whatsoever. Did HG about 2000 miles ago because they were clearly worn and leaking externally but has not had any loss or burning since. The 2005 has around 140k miles on it and the 06 has over 200k.

 

[Ozark_SyntheticsLLC]

Blkwolf87 Welcome to the forum.
With your extensive background information of working with your dad on Subaru's is a great addition to the forum.

After reading both of your post I am at a loss also as to where the oil is coming from and why you would be burning oil unless the deck on the block was wrapped and causing the oil to pass by but then you would have terrible compression.

I am going to follow this to try and learn something new as to why this is happening. Good Luck and keep us posted.

 

[Blkwolf87]

Blkwolf87 Welcome to the forum.
With your extensive background information of working with your dad on Subaru's is a great addition to the forum.

After reading both of your post I am at a loss also as to where the oil is coming from and why you would be burning oil unless the deck on the block was wrapped and causing the oil to pass by but then you would have terrible compression.

I am going to follow this to try and learn something new as to why this is happening. Good Luck and keep us posted.

Thanks for responding. The only thing I can of is maybe the rings on the dipstick are allowing air flow through that, I guess I could clean or replace the pcv hose instead of just cleaning the pcv valve, or ya a warped deck maybe. And as I said it’s only visibly noticeable when I have high rpms getting onto the freeway. During city driving it might not be enough for me to see. So I’m at a loss. Unless maybe my oil pump is the issue idk it’s driving me crazy though

 

[Blkwolf87]

Thanks for responding. The only thing I can of is maybe the rings on the dipstick are allowing air flow through that, I guess I could clean or replace the pcv hose instead of just cleaning the pcv valve, or ya a warped deck maybe. And as I said it’s only visibly noticeable when I have high rpms getting onto the freeway. During city driving it might not be enough for me to see. So I’m at a loss. Unless maybe my oil pump is the issue idk it’s driving me crazy though

I’ll do a new compression test Monday. I should’ve done so after changing the pistons, rings, and stem seals

 

[Blkwolf87]

Here’s what my old pistons looked like when I removed them

 

[Blkwolf87]

Blkwolf87 Welcome to the forum.
With your extensive background information of working with your dad on Subaru's is a great addition to the forum.

After reading both of your post I am at a loss also as to where the oil is coming from and why you would be burning oil unless the deck on the block was wrapped and causing the oil to pass by but then you would have terrible compression.

I am going to follow this to try and learn something new as to why this is happening. Good Luck and keep us posted.

So I did a vacuum test on my pcv valve and found it’s toast. So during high acceleration getting onto the freeway it’s wide open sucking the most vacuum and pulling oil into my intake manifold. Can’t believe it was such a small cheap freaking part.

 

[Ozark_SyntheticsLLC]

Those piston heads look great! I don't see a problem at all ...(said every shade tree mechanic)

The cheapest part is always the problem, why do we always want to do the most expensive thing first?

Glad to hear you go it fixed, now time to put another 100K on the Subaru!

 

[Blkwolf87]

Those piston heads look great! I don't see a problem at all ...(said every shade tree mechanic)

The cheapest part is always the problem, why do we always want to do the most expensive thing first?

Glad to hear you go it fixed, now time to put another 100K on the Subaru!

Number 3 was actually kinda loose and had more movement than it should’ve. So that’s why I did those plus the valves for that cylinder had build up and needed to be cleaned. As you can see in the second picture you can see the two lines where the oil was bypassing the rings as well. I know some of that is normal wear do to the sideways motion of the pistons but it had a puddle of oil in that cylinder upon removal. I’m hoping the new pcv will take care of the oil burning issue. If not I’ll eventually scrap this block and get another

 

[Ozark_SyntheticsLLC]

Yea I hope that solves the problem. It stinks that it took all of that work and troubleshooting to get to this point. Good work on the car though. Let us know if the PCV valve fixes it.

 

[Blkwolf87]

So it’s still poofing smoke out the back when I accelerate hard getting onto the freeway. Idk what else to do other than maybe the two rings of the dipstick tube are worn and causing it suck air through that and pulling oil up the pcv. I’m not taking it to Subaru because they charge up the wazoo to do the oil consumption test. The tech advisor obviously can’t tell anything unless I brought it to them. Idk wtf else to do with this engine other than replace it if the dipstick rings are that’s left that I can think of. I’ve talked with multiple other Subaru experienced mechanics and they don’t know either. Aaaaahhh anyone else that has anything else that we haven’t thought of PLEASE HELP

 

[Blkwolf87]

Omg I think I might’ve finally found the last culprit to my oil consumption issue. Bad/Worn oil dipstick tube rings. Makes sense since the pcv system into the intake manifold has vacuum on it; it’s sucking air past those thus pulling oil into the pcv then into my combustion chamber causing the plum of grey/blue smoke out the exhaust. Will post tomorrow after my drs appointment since I generally see it as I get on the freeway.