Excessive Oil Consumption

[skeeter]

I have a new to me 94 Legacy 2.2 with 102,000 miles on the engine. I just took it on a 3,000 mile trip to the mountains and found that it burned 1 quart of oil per 1000 miles on the way out and 1 quart of oil per 500 miles on the return trip. My last Subbie (85 GL Wagon) went several hundred thousand miles with little engine trouble. What are the most likely causes of this type of oil consumption?

[1 Lucky Texan]

I doubt that I'd have any clue either but i will offer a suggestion or 2 based on what I've read.

Sometimes a bad/dirty PCV valve/hose can cause pressure to build in the crankcase and camcovers. Any small seepage will leak more due to the pressure.

Sending in an oil sample for analysis might help tell the ring conditions. They would allow more blowby if worn and the oil would have more fuel and combustion byproducts than normal. But starting with normal compression and 'leak down' tests would likely help as much. You don't mention leaks or seepage. Do a search on these forums and you will find the common seals and oil pump backplate leaks mentioned. If the cars has only a few spots, but from different areas under the vehicle, you most likely have a leak only when the oil is pressured up and during driving it is being sprayed back onto the undercarriage to drip randomly when you stop. I had this problem 3 times on 2 cars (non-soobs) due to leaking oil pressure senders.

You also didn't mention anything about the cars prior service history. perhaps it was abused? If indeed you have bad valve seals or rings, do use a slightly higher viscosity oil but DO NOT think it can go longer between changes because you have to 'top up' frequently. It will become contaminated with fuel and need to be drained.

[Setright]

PCV system is the first place to look. No matter what, replace the PCV valve. At the same time make sure all the PCV hoses and connections aren't blocked - they rarely are, since they have quite a large diameter.

 

My car drinks from one to two quarts between my 6000 mile changes and this is what I would consider normal and healthy. Especially at 188,000 miles

 

(Mobil 1 5W-50)

[Legacy777]

what type of oil you running?

[applegump]

Can anyone give me the subaru part number for a PCV valve for a '90 Legacy 2.2?

 

Thanks!

[skeeter]

Thanks for the help. I just replaced the PCV Valve (Fram part #FV277) but the old one looked OK. The hoses were not plugged either. I am using Valvoline 10W30 oil here in the Minnesota Winter. I'll watch the oil closely to see if anything changes. Any other ideas?

[Setright]

DOH! Applegump, you should've asked like day earlier and I would still have had the reciept for mine....surely the dealer can look it up?

 

 

Even thought the PCV valve looks OK, the spring may be weakened, and the barrel worn, and therefore not seal well. After a drive, open the hood and try to pull the dipstick out. It should require a firm tug the first time. The stick should get pulled in by vacuum in the crankcase if the PCV system is working.

[Supaglu]

Hi,

If you shake the old PCV valve and it rattles - then its ok !.

 

One thing comes to mind regarding the piston rings, during the normal course events - all the pistons rings rotate around the piston but what sometimes happens is that one or other of the three rings on one piston will stick and the other rings will rotate so that all the ring gaps line up - if your unlucky then they might stay like it.

As already suggested a compression test or leakage test will confirm this.

 

Regards

Dave H.

[intrigueing]

You have any external oil leaks? I would tend to guess leakey cam/crank seals that could be consuming your oil. The seals tend to go south around 100K - Rings do not - 100K is barely even broken in for the 2.2.