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Discussion Starter #1
I was hoping I could get some help/advice regarding my Subaru Outback 2.5 SOHC (EJ251) 2000.

It is a donor engine that needed the head gaskets replacing. Before I put this engine (which has done approx. 128K miles) I replaced the head gaskets, had the heads skimmed, checked, cleaned, valve re-seated and new valve stem seals fitted by a local very good engine company. I also replace the cambelt, oil/water pump, pulley, plugs, leads ect ect while it was out.

The engine is running great however it is using SOO much oil, it has used about 3litres (over 3 quarts of oil) in a little over 500miles. There are ZERO external oil leaks and it is dry as a bone on the external. Yes it does smoke (mainly White’ish) on start-up but not excessive and even under full throttle it not particularly noticeable. It does smell very rich.
It pulls well and no loss of power – I have checked the compression before however I can remember what the number were but they were all well within 5% of each other which I believe is important part of a compression test.
I have tried using thicker oil (as far up as 15/50- I live in the UK) and have also checked the PCV valve and replaced twice to be sure with OEM ones.

So any help/guidance would be great – I am thinking it has to be either worn compression or oil control rings or badly installed/incorrect valve guide seals but I am hoping somebody could help me find the issue.
 

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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Most likely that donor engine needed more than just an HG job - probably the piston skirts got scuffed badly at some point (an overheat), or the oil scraper rings are stuck, allowing oil to bypass them and get burned. In either case, this should show on the plugs.

You might try treating the oil with Seafoam ( if it is available over there) to see if it will free up the oil scraper rings.
 

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I simply cannot abide useless people.
2006 2.5i and 2002 3.0 wagons.
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If you're eating 3 quarts in 500 miles of 15W50, there are serious mechanical issues needing to be addressed. I'd say the rings are probably shot, or something did not get reassembled correctly.
 

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Discussion Starter #4
Most likely that donor engine needed more than just an HG job - probably the piston skirts got scuffed badly at some point (an overheat), or the oil scraper rings are stuck, allowing oil to bypass them and get burned. In either case, this should show on the plugs.

You might try treating the oil with Seafoam ( if it is available over there) to see if it will free up the oil scraper rings.
Thanks for the quick reply m8 - really appreciate it.

I have thought it could be stuck/work oil control rings. I am assuming that if is was the oil control rings this would not show up on the compression test as that is only testing the compression rings???


Also you mentioned wear to the piston skirts, again I have read a lot of info on the skirt slap issue however I dont understand how worn piston skirts would increase oil consumption???
 

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'03 outback limited, '01 Outback Limited, '01 Legacy L wagon, '96 Legacy Brighton wagon
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Well, if the skirts are scored and worn, the pistons will tilt more than they should in the cylinders, allowing the scraper rings to tilt more than they should as well, and not seal correctly.
 

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probably needs new rings.

you can replace the rings without splitting the block, so it could be repaired.

piston rings causing oil consumption is common, but you're seeing some massive losses for sure.
 
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