Where is the oil going?

[jeryst]

1998 Legacy Outback Station Wagon. 2.5 motor. 127k miles.

 

I bought the car back in January, and it runs great. I put new

spark plugs and wires on it. It had new timing belts put on right

before I bought it. The people that I bought it from only used it

as a back up vehicle, so they didnt drive it a lot.

 

When I first got the car, it was using about a quart of oil every

500 miles or so, which I didnt think was too bad for a 20 year old car.

 

Recentlt, however, the oil consumption has increased to a quart every

300 miles. I have parked the car on clean pavement, and let it sit, both

running and not running, but have not seen any signs of a leak. No

smoke is visible coming from the tail pipe when idling or while driving.

There is no oil in the coolant system.

 

You would think that if the car was burning a quart of oil every 300 miles, smoke would literally be billowing from the tail pipe as I drive. I've had cars with cracked rings that looked like I was crop dusting, and they didnt use a quart every 300 miles.

 

So my question is: Where is the oil going?

Could it be burning the oil so completely that it is not visible?

[idosubaru]

Yes you’re burning oil. It’s not so much being about burning completely as it’s an insignificant amount, in those terms.

 

Go to your kitchen and divide up an itty bitty teaspoon into 10,000 equal parts. That’s how much oil you’re burning per revolution. 1 quart per 300 miles is like 1 quart per 1 million revolutions. It’s nothing. It’s so small you can’t even do it with an eye dropper.

 

In these terms it’s not surprising you don’t have symptoms. There are different failure modes and mechanical differences across models but doesn’t matter, unfortunately your rings are shot.

Edited April 27, 2018 by idosubaru

[idosubaru]

I’d run 20w-50 in the summer. I know people will faint to read that so try 10w or 15w and see if that slows the bleeding.

[montana tom]

Unfortunately that year motor is known for poor rings. You need at least new rings and possibly there is a better year piston design  to use.  G.D.) would have that info.

EDIT)  My bad its the 2.2 in 99 with ring issues.

Edited April 27, 2018 by montana tom

[GeneralDisorder]

Replace the PCV valve with one from the dealer.

 

GD

[jeryst]

I’d run 20w-50 in the summer. I know people will faint to read that so try 10w or 15w and see if that slows the bleeding.

I am currently using 10w-30. I still dont understand why I cant see smoking or leaking.

[jeryst]

Yes you’re burning oil. It’s not so much being about burning completely as it’s an insignificant amount, in those terms.

Go to your kitchen and divide up an itty bitty teaspoon into 10,000 equal parts. That’s how much oil you’re burning per revolution. 1 quart per 300 miles is like 1 quart per 1 million revolutions. It’s nothing. It’s so small you can’t even do it with an eye dropper.

In these terms it’s not surprising you don’t have symptoms. There are different failure modes and mechanical differences across models but doesn’t matter, unfortunately your rings are shot.

I've had cars with worn rings and cracked rings and they always smoked a lot, so I

guess it just seems strange to me that there is no smoking with this amount of oil

consumption. But I guess it has to be burning if its not leaking.

[jp98]

Check for the smoke at night with enough light to see. 

 

I would wager that you will see the smoky haze.

[Gloyale]

Replace the PCV valve with one from the dealer.

 

GD

 

+1

 

 

Also.  to see if the oil is being burned.

 

First, clean the tailgate really well.  then go for a few drives (not on gravel roads)  

 

Now take a clean, white, paper towel and wipe the area of the tialgate just directly above the exhaust.  Oily residue?  black?   Compare to a wipe from the other side of the gate or even the side of the car.

 

This will likely show that at least some oil is being burned.

Edited April 27, 2018 by Gloyale

[Rooster2]

Agree, that changing the PCV valve could be a big factor in reducing oil usage. That is very easy, and cheap to do. You may want to change the brand of oil that you are using. Sometimes, certain oils burn up quicker then others.

[idosubaru]

A PCV would cause seventeen quarts of oil between 5,000 mile oil changes?

Edited April 27, 2018 by idosubaru

[idosubaru]

I've had cars with worn rings and cracked rings and they always smoked a lot, so I

guess it just seems strange to me that there is no smoking with this amount of oil

consumption. But I guess it has to be burning if its not leaking.

Blowing smoke is the outlier rather than asymptomatic oil usage. It’s easy to see - google “oil consumption issue” and see all the modern vehicles that consume a lot of oil and you won’t see any of them blowing smoke. Thousands and thousands of them, they’re common across various manufactures, aren’t billowing clouds, and ubiquitous as flies.

 

there are various failure modes, manufacturers, materials differences, and varying ring set ups.

[Gloyale]

A PCV would cause seventeen quarts of oil between 5,000 mile oil changes?

it can.

 

And also, an off chance, but the O-ring that seals the PCV "drain back" tube inside the oil pan at the rear corner can be an oil use issue too.

 

If that o-ring doesn't seal, then oily vapor near the pan gets pulled up into PCV, rather than being the drain back for the PCV.

[GeneralDisorder]

A PCV would cause seventeen quarts of oil between 5,000 mile oil changes?

I've seen all 4 quarts go through a junk aftermarket PCV valve in 100 miles.

 

GD

[GeneralDisorder]

If that o-ring doesn't seal, then oily vapor near the pan gets pulled up into PCV, rather than being the drain back for the PCV.

That isn't one I've seen. On the contrary the aftermarket pans by Killer-B and others have no provision for this seal. None of the built engine that we have done using this and the Moroso pan have had any significant oil consumption due to their designs not incorporating the snorkel pipe.

 

GD

Edited April 28, 2018 by GeneralDisorder

[jeryst]

Could it be the oil pan itself? I had the oil pan replaced when I got the car

because it was "weeping". The replacement was aftermarket, not Subaru. The oil

consumption may have increased after that, come to think of it.

[jeryst]

Is there a good aftermarket replacement PCV other than an actua Subaru part?

Edited April 28, 2018 by jeryst

[idosubaru]

I've seen all 4 quarts go through a junk aftermarket PCV valve in 100 miles.

 

GD

 

wow, if it wasn't you i wouldn't believe that at first glance!

 

this joker fixed it before he missed one morning oil top off before work...his odds weren't in his favor. 

 

makes me want to stuff a PCV hose shut and see what happens for a 100 miles just to see it myself.  i've got a running and driving 03 going to the scrap yard, it's tempting. 

[idosubaru]

Is there a good aftermarket replacement PCV other than an actua Subaru part?

 

nah, get the OEM one from subaru.  they're way cheaper than all this oil the car needs to run. 

 

$12 paypal and i'll ship you one. 

[GeneralDisorder]

Is there a good aftermarket replacement PCV other than an actua Subaru part?

Not that I'm aware of. A customer of mine (another shop) bought a good used engine from me. I resealed it and they installed it. They bought two parts without asking me - an air filter and a PCV valve. Both from Autozone. Engine ran dry of oil in 200 miles and rod knocked. No visible exhaust. They filled it up with oil and took it for a test drive with a follow vehicle to look for smoke and there was none they could see. It used an entire quart in about a 20 mile test drive. Upon tear down it was fairly obvious the PCV hose from valve to manifold was the oil source.

 

Autozone ended up replacing the engine. They agreed with our analysis and so did the manufacturer of the valve (Wells). Though initially they denied the claim stating the customer should be checking her oil. It was an older lady in her 70's so that just wasn't going to happen.

 

GD

[Gloyale]

That isn't one I've seen. On the contrary the aftermarket pans by Killer-B and others have no provision for this seal. None of the built engine that we have done using this and the Moroso pan have had any significant oil consumption due to their designs not incorporating the snorkel pipe.

 

GD

 

Forced induction on those engines? kinda changes PCV dynamics a bit.

 

I know I had an engine that made black clouds it burned so much oil, but ran perfectly.  165k mile 2.2 in a 93 legacy.  Replaced PCV with subaru one, still burned oil.

 

Resealed the pan and that O-ring inside it at the back.....smoke and oil consumption stopped.

 

Can't say it's this posters problem, but it is something I always consider now when looking into oil consumption/smoking engine.

[DaveT]

Burning a quart per 300 miles is not enough to make visible smoke.

I had an EA82 that was doing that.  It had been overheated pretty badly, It had no knock or any other bad symptoms, so I resealed it, but didn't think of checking the oil rings.   It even passed emissions.  I ran it for years on used oil and whatever cheap oil I came across, until one of the heads cracked.

[GeneralDisorder]

Forced induction on those engines? kinda changes PCV dynamics a bit.

 

I know I had an engine that made black clouds it burned so much oil, but ran perfectly. 165k mile 2.2 in a 93 legacy. Replaced PCV with subaru one, still burned oil.

 

Resealed the pan and that O-ring inside it at the back.....smoke and oil consumption stopped.

 

Can't say it's this posters problem, but it is something I always consider now when looking into oil consumption/smoking engine.

Interesting. Funny notation to that seal though - silicone garden hose washers are a perfect fit and will never go hard. Also cheap in bulk.

 

GD

[jeryst]

Forced induction on those engines? kinda changes PCV dynamics a bit.

 

I know I had an engine that made black clouds it burned so much oil, but ran perfectly.  165k mile 2.2 in a 93 legacy.  Replaced PCV with subaru one, still burned oil.

 

Resealed the pan and that O-ring inside it at the back.....smoke and oil consumption stopped.

 

Can't say it's this posters problem, but it is something I always consider now when looking into oil consumption/smoking engine.

 

So do the aftermarket pans just not have a place for the seal? Sorry, but

I'm a little confused about the pan issue.

[jeryst]

nah, get the OEM one from subaru.  they're way cheaper than all this oil the car needs to run. 

 

$12 paypal and i'll ship you one. 

Sorry, I ordered one before I saw your post.

Thank you for the offer, though.