Weird oil issue

[jeryst]

A while back, I started a post about oil usage in my 1998 Legacy Outback wagon with the 2.5. my issue was that it was using a quart of oil every 300 miles, but it was not leaking it, or visibly burning it.

Recently, I started to check it daily, and noticed something that seems weird to me.

I travel 160 miles every weekday, round trip 

I add oil until the level is at the full mark before I go to work on Monday morning.

Tuesday morning I check the oil, and the level is down just a little bit.

Wednesday morning the level has dropped a significant amount to the Fill mark.

Why does it only seem to use a little bit of oil on the first day, and then a lot of oil on the second day?

Is it the shape of the oil pan or something like that?

 

[idosubaru]

The top of the pan does have more volume and the lower portions have baffle plates taking up space.  

So theoretically the level will drop at different rates on the dipstick for the same rate of volume loss.  

At first guess it seems it may indeed loose it “slower” at first due to volume and baffle plates mentioned above. But I have no idea how much that is, or if it’s even practically significant.  

Either way, an eggregious oil leak is obviously a problem that’s not going away. 

[idosubaru]

I would guess if you fill it every day or every two days you’ll have the same oil consumption. But since it’s loosing so much you can test it and know by the end of the week. 

[db*****]

I know there is an o ring in the oil pump that can leak, my 99 ej25d has similar symptoms, and I know on that engine the oil pump o ring leaks. Either way sounds like a significant oil leak 

Edited September 26, 2019 by db*****

[idosubaru]

1 hour ago, db***** said:

I know there is an o ring in the oil pump that can leak, my 99 ej25d has similar symptoms, and I know on that engine the oil pump o ring leaks. Either way sounds like a significant oil leak 

The oil pump can't leak in a way that oil doesn't leak externally thought right?  If it's not dripping on the ground then I don't think there's anyway the oil pump can "consume" it. 

[el_freddo]

1 hour ago, idosubaru said:

The oil pump can't leak in a way that oil doesn't leak externally thought right?  If it's not dripping on the ground then I don't think there's anyway the oil pump can "consume" it. 

Correct. It’s an internal leak and a loss of oil pressure. 

@jeryst - you’re using synthetic oil? If so, you won’t see that burn like mineral oil. 

Cheers 

Bennie

[idosubaru]

2 hours ago, el_freddo said:

 

@jeryst - you’re using synthetic oil? If so, you won’t see that burn like mineral oil.

Oh really?  I didn’t know that, interesting. 

Edited September 27, 2019 by idosubaru

[jeryst]

I just use regular oil, not synthetic.

The car does not leak a drop, not even valve cover gaskets. Does not smoke. No film on the back windowor tailgate.

I need to add a quart after every two days of driving to work, like clockwork. It does have 161k miles on it.

[forester2002s]

Try changing the PCV valve. (use Subaru OEM only).

[el_freddo]

7 hours ago, idosubaru said:

Oh really?  I didn’t know that, interesting. 

I read it on another forum and it made sense to us as mum’s corolla was using oil like no tomorrow but we couldn’t see it burning and it wasn’t dropping it - and it was running on full synthetic oil. We assume the oil rings were shot and it was burning it all off.

And for those wondering how much, about a litre for every 400-500km (country driving, not start/stop city driving). 

Cheers

Bennie

EDIT: think about all these new cars running low friction rings, using oil between changes - you don’t see them burning oil! Not how they used to run them!

Edited September 27, 2019 by el_freddo

[Rampage]

You or your mechanic should check out the piping from the PCV Valve down to the Block. The rubber hoses get very hard and the plastic y gets brittle, so taking them apart can be a chore. I did brake the y one time. Best to replace the hoses with new.

Check the inside of the y and the hoses, also the hose from the y down to the block. With the gases and oil coming from the crankcase, they build up crud on the inside and the passage becomes smaller. With the passage becoming smaller the air flow moves faster and will tend to take more oil with it to the intake to be burned. With the higher rpm of driving you have more leakage past the piston rings thus more pressure in the crankcase to make its way through the PCV valve.

I have removed intakes and had oil run out when tilted.

[jeryst]

13 hours ago, Rampage said:

You or your mechanic should check out the piping from the PCV Valve down to the Block. The rubber hoses get very hard and the plastic y gets brittle, so taking them apart can be a chore. I did brake the y one time. Best to replace the hoses with new.

Check the inside of the y and the hoses, also the hose from the y down to the block. With the gases and oil coming from the crankcase, they build up crud on the inside and the passage becomes smaller. With the passage becoming smaller the air flow moves faster and will tend to take more oil with it to the intake to be burned. With the higher rpm of driving you have more leakage past the piston rings thus more pressure in the crankcase to make its way through the PCV valve.

I have removed intakes and had oil run out when tilted.

I already changed the PCV valve. I will have to check out the Y and tubing.

[1 Lucky Texan]

I have read on occasion that some car's oil control rings can be helped with marvel Mystry Oil. I don't know the procedure.

I would start with the PCV valve mentioned above. And, if major work was ever done or the engine out - double check PCV and breather hose routing.

[Rampage]

1 hour ago, 1 Lucky Texan said:

I have read on occasion that some car's oil control rings can be helped with marvel Mystry Oil. I don't know the procedure.

I would start with the PCV valve mentioned above. And, if major work was ever done or the engine out - double check PCV and breather hose routing.

Wow, that brings back memories. In the early 60s I had a 51 mercury coup with a flathead V8. It had a Marvel oiler on it. The tank mounted on the firewall and an aluminum tube ran down to a plate mounted between the carb and intake. There was a site glass on the tank and you could adjust the flow of the Marvel Mystery Oil for one drop a minute or something like that.