Oil overfill possible implications

[timbercomp]

G'day!

We've recently bought an SF forester, 5sp manual, 2.0 NA and its been going well. Seems to go really well.

I've checked (and rechecked) the oil level and it looks like its a long way above the maximum marking... I know the previous owner had reported some oil weeping from rocker covers and maybe a cam seal (somewhere... sorry to be vague). Anyway, I plan to replace rocker covers when doing the timing belt in the coming weeks, and whatever cam seal needs replacing too... But I wonder if there is anything else that is possible/likely to have gone wrong with a too-high oil level?

Any other things to look out for while tinkering with a c.200,000km EJ20 would be great to hear about, too.

Thanks in advance

 

[Kevin]

I think it has to be a very long way over to do any damage; when my car was serviced by Subaru it was always overfull. When doing the rocker covers also do the seals for the spark plug tubes. On the front end when doing the timing belt you'll be able to check around the cams, crank and oil pump for leaks.

 

[timbercomp]

That's excellent news, thanks so much Kevin. Will take a good look, and do the seals you mention.

 

[Dulagarl]

Possible implications (from experience)

• excess oil in crankcase can vapourise;
• gets let of through PCV valve into fuel intake
• deposits oily gunk into air / fuel intake
• gunks up throttle body
• gunks up oxygen sensors
• potentially gunks up catalytic converters.

I had this problem recently from overfilling. Remedy was to get oil to correct level, clean throttle body, remove and clean PCV valve, remove and ultrasonic clean oxygen sensors, hope that cats aren't stuffed.

For some time after this I was getting sooty deposits out of the exhaust when cold / cool. Seems to have cleaned up now.

Do not overfill your oil!

 

[Rally]

Depends on by how much. On the race track, a bit of overfill is done to counter oil surge in corners.

 

[Ben Up North]

When filled according to manufacturers specifications my SG always shows above the max oil mark, and it's been pretty much like that it's whole life (coming up to 14 years old, 166,000ks) without any problems. We don't drive it particularly hard though - if that matters.
I must remember to ask the mechanic to put in slightly less when he services it. see if it makes a difference. He won't be keen though, he's pretty anal about ssticking to manufacturers specs.

You could always shorten your dipstick a bit. (please note: this was an attempt at humour, please don't actually do this.)

 

[Kevin]

:lol:

 

[duncanm]

the shape of the EJ sump (narrow and deep) means the dipstick measure is more sensitive to oil level than a typical inline or V engine.

Rocker gaskets always get weepy as they age - probably just need replacement.

If it doesn't burn oil or make noises, probably good to go.

Don't forget the obligatory water pump and tensioner when you do the timing belt.

Probably also worth replacing the spark plug seals.

 

[Kevin]

Now my turn to have an overfilled engine.

If the oil is overfilled to the twist above the maximum mark on the dipstick could it blow an oil seal? I wouldn't have thought so but:

I took my Foz for it's first (110 klm/hr) motorway run since a major service in March; all was well until I got back home and discovered oil leaking from the bottom of the timing cover. As it had lost some engine oil I checked the level when cold and it is overfull.

They did repair a rocker cover leak when being serviced that "dripped" from the bottom of the timing cover and it never got past the sump guard whereas this one spilled over onto the concrete which is how I noticed it. I thought it was an air conditioning puddle at first.

The car is now back at the workshop awaiting repair. Will be interesting to hear what they have to say!

 

[Kevin]

BTW - the car ran really well on the run.

I've just heard from a Subaru Senior Master Tech about the overfill:
"Realistically, i doubt it could cause an oil leak.
In order for it to cause a leak, it needs to build up a lot of pressure, and the engine has room to expand the oil. "

 

[ABFoz]

I think it's OK. I believe Subaru and many newer engines have good enough tolerances for overfilling. I haven't heard of Subarus getting windage issues or aeration, probably because the design requires for more tolerance as the cylinders are flat. With the flat orientation of the cylinders, by design, the piston rings must seal/control oil better as they get in contact with oil more vs inline and V-type engines.

Overfilling reduces the overall oil pressure and distorts overall oil flow making the engine work a bit harder but the worst complication I have heard about is just more oil in the combustion chamber resulting to bluish smoke in the tailpipe. I remember seeing it on a 7AFE engine but after bringing the oil to the correct level, the issue was solved.

It can be a bit worrying if it's done on a turbo direct injection engine as the higher blow-by of the engine design dilutes the oil more. When such engine is overfilled, the oil gets diluted faster. Cheers.

 

[Kevin]

Got the car back yesterday; was a crank seal and the work was performed for no charge and also confirmed that oil at that level is fine but if it's still at that level when cold I will drain a little out (with the Fumoto valve)

 

[subyroo]

The Maroochydore Subaru Dealership always filled my 2000 RX Liberty & 2003 XS Forester to the same level as Kevins picture at post #9.
I bought my a little hand pump with a hose that fitted down the dipstick, I would take out the extra oil until it was a fraction (mm or two) over the full mark.
I ended up moving to Boxer Service in Brendale (Bne) for all my servicing and repairs, could not have made a better move.

If filling with oil above the full mark on the dipstick does not matter, why have a Full mark in the first place?
Why not just have "fill with a minimum of X number of liters" and be done with it. Just have the min mark on the stick.