I've just taken my 250t (1995 EJ25D) for it's first big drive after sealing it up and putting a manual trans behind it. Did about 1000km (~600miles) and it went through about 2 litres (~~2quarts) of oil!! (of course I was topping it up along the way!).

 

I steam cleaned the engine & surrounding area when I had the engine out, and everything still looks clean. It used to go through a fair bit of oil, but I attributed that to teh leaking cam seals, which were leaking all over the exhaust and making a big mess.

 

Looking out the back when driving, I haven't noticed any smoke, but I haven't got someone to drive behind me yet.

 

Could a bad PCV valve cause this much oil consumption? Seems excessive to me...

I don't think an ailing PCV valve would cause that much consumption. I would look for other sources of leaking.

I have seen failed PCVs cause > 1Qt in 500 miles oil consumption, but that wasn't on a Subaru. Rather than speculating, why not check and or change the PCV valve and see what happens?

It's really not leaking. I have checked the bottom of the heads, the oil pan, and the front face of the flywheel, and they are all totally clean. So is the engine cross member. If it had leaked out two litres it'd be very noticable....

 

If a PCV valve can indeed cause such significant consumption, I'll certainly go ahead and replace it. Just don't see much point if there is no way it could cause it......

Are you sure you are reading your dipstick properly? I have done this multiple times the angle of the car and time the car was sitting is crucial for reading the dipstick properly.

Yep, I've had trouble with these in that way before too -- they do seem very sensitive to changes in angle etc. But I've checked this multiple times on a number of level surfaces with the same results. And we're talking about nearly half the entire capacity of the engine oil going missing too, not just a few hundred ml.....

OK, so the hose going to the PCV valve is full of oil, so it does look likely that it's the culprit. I'll replace the valve before the next road trip in a week and see how it goes....

New PCV valve helped, but not a lot. The PCV hosing is still full of oil, and it's still burning at least 1l/1000km. There are no leaks. Never see any blue smoke. Is this engine just breath-ey due to it's old age, or could something else be going on? I'm going to try a catch can in the PCV system next.

Something doesn't seem right, there will be some oil in the PCV hose, but the PCV valve is supposed to stop it from entering the intake. So either the PCV valve is not working properly, or there is something causing a LOT of oil to be pushed up into the separator, more than it can handle, and it is being sucked up into the PCV hose. Excessive blow-by is the primary cause of this.

 

Check the routing of your breather hoses. Make sure they are all free of obstruction, not kinked, and connected tight where they should be.

There is a small hose that leads off the PCV hose connector. I don't know where it goes to but make sure it is clear as well.