Oil is not oil. In today’s engines, oil not only lubricates, it is used as hydraulic fluid and coolant. As hydraulic fluid, it controls your variable valve timing, and with a turbo, it cools the main bearing. Your engine requires a synthetic oil because it is more resistant to the very high temperatures of the turbo bearing. If you are using non synthetic or synthetic blend and only changing every 6k, I’m surprised that your turbo is still functioning.
I’m not opposed to SuperTech as a brand, but you need to use the full synthetic oil of the proper grade and because you have a turbo that generates a lot of heat, it has to be changed much more frequently. The sludge is evidence that you are either not using synthetic of the proper grade or not changing it as frequently as you should, or both. This engine is not prone to sludging if you did.
The sludge also indicates this horse has been rode hard and put away wet more than a few times, but that’s why you bought it, for the fun factor.
I would have a compression test done. If there’s no/low compression then oil likely getting past the rings and the engine is more or less done. If the compression is good, then it’s likely being inhaled through the PCV valve
While they have the engine apart, this would be a good time to tell them that you want to see it for yourself.
If it does indeed have a sludge accumulation, that is proof that your oil changes were not done often enough, and that you erred by NOT using the specified full-synthetic oil.
And, while I don’t want to beat a dead horse, your Owner’s Manual/Maintenance Schedule clearly states the full-synthetic oil requirement as well as the 3,750 mile oil change interval that is required with their turbo engines. It really does pay to read–and follow–the documents that a vehicle mfr provides.
Frankly , what one of us would do is not really going to help you. I don’t know if you are the only one making this decision or if you have a significant other. Only you know your comfort level on major expenses . Decisions like this are made in our house by the two of us, not that we always get it right but at least we have no one to blame.
The engine sludge is there because you did not change the oil often enough both as to time and miles.
Tear the engine down and you will find the oil control rings frozen.
As for Wal Mart oil, I’ve been using it for well over 20 years on everything and have never experience a sludge issue on anything i’ve owned even at 300k miles and more. Then again, I change oil every 3-4k miles and most of my miles are on the highway. Just lucky I guess.
I saw the sludge for myself, my fault for assuming it’s oil changes was like a regular run of the mill car.
Appreciate the link @keith I’ll check and see what they think as well.
I did a compression test and found 1. 164psi 2. 168 psi 3. 153psi 4. 170psi. So there’s really only a difference of 17-18psi which I would think is quite negligible. The wet run was about the same 1. 165 psi 2. 168 psi 3. 163 psi 4. 171 psi.
The turbo main bearing also feel tight as well and spins freely. No noticable chips in the turbine, just quite a bit of carbon on the exhaust side of everything.
A compression test won’t tell you the condition of the oil control rings. They can easily be stuck as ok4450 says and you’d still get good compression readings.
With all that sludge in the valve covers you obviously have a lot of oil dwelling in the top of the engine. If it sits up there it will certainly overwhelm the valve seals, even good valve seals, and run down the valve stems to be burned. Valve seals are not designed to control oil pooling in the head.
You may be able to correct the oil burning by just getting the heads cleaned out and the valve seals replaced, but then you’ve still got an engine full of sludge, along with what is probably going to be ruined catalytic convertor(s).
For a Subaru those compression numbers are abnormally low. They should be in the 190ish or so range.
As JayWB says, a compression check won’t reveal anything about the oil control rings. He is also correct about oil pooling in the cylinder heads and leakage past the valve stem seals. And the catalytic converters…
Pcv problems can cause major oil burning. Since you know you got that problem, before assuming the problem lies elsewhere, fix the pcv system and measure the oil burn rate after that.
My vote is for changing the PCV to see what happens.
Generally speaking, when the compression numbers do not go up much during a wet compression test this means low compression is caused by an issue with the valves.
The mileage is a bit low to experience cylinder head valve problems. It would also be very unusual to happen on all cylinders; unless someone in the past had misadjusted them to where the lash is zero. That’s not unheard of as some people don’t like the tick sound and adjust them to zero to shut them up. Big mistake of course.
I would go a step at a time, starting with the least expensive.
Fix the PCV system: replace the valve and clear the hose and vacuum port.
That might reduce the oil consumption to a level you can live with without spending $$$.
Do a series of short oil changes, 1-2000 miles with synth oil.
Pray the computer doesn’t throw a cat conv error code.
Oil doesn’t pool on these heads like most engines, at least not in the same way as the top of the heads are vertical instead of horizontal. But it can pool near the drain back holes and if enough sludge builds up here, it can block the drain back passages and that can cause the amount of oil consumption you are experiencing.
If they are blocked, then it is highly likely that your oil control rings will be carboned up as well.
My recommendation for a cheap fix that might work, clean all the visible crud off the tops of the heads. Run a 1/2" dia round brush down the drain back passages to make sure oil can return back to the oil pan. Replace the PCV valve. Use a high detergent full synthetic oil of the lightest recommended grade. If your engine calls for 0W20, use it. Pennzoil claims to be one of the highest detergent oils but I believe that Mobil 1 EP is also very high detergent. Change it at 500 miles first change, but add a quart of diesel fuel or kerosene and run for 5 minutes before changing the oil. Next change 1000 miles later and repeat with the diesel or kerosene (or Motor Flush). Do a third oil change 1000 miles later if the oil consumption is back to normal and then every 3k after that with any good full synthetic of the proper grade. Even SuperTech will be OK.
If the oil consumption has not returned to normal before the third oil change, you will need a new motor.
Edit: I would not worry about the valve seals in a motor of this design. If the above doesn’t fix the problem, you will need a lot more than valve seals. Oil doesn’t normally pool around the valve stems in this motor as far as I know. The guys at the Subaru forum would know more about this.
SeaFoam or SuperTech generic for it will work better and safer than diesel/kerosine.
Some people also recommend idling the engine for 5 minutes, then letting it sit/soak for 5-10 minutes, then starting and idling for another 5 minutes, then following with drain/refill.
Also, SuperTech has “full synthetic”, it’s cheap, I’ve tried it once, but I was not happy with oil burn rate my Subaru showed at a time, so I’ve returned back to Valvoline, burn rate immediately returned to normal.
That’s how I inherited my first car from my father: it was getting through 5-6 quarts of oil every 1000 miltes, mostly dumping it on the ground via various leaks, mostly on gaskets and seals.
When I asked him when he changed oil last time, the answer was “no need, I have it replaced automagically”
Once I re-sealed the engine, it dropped to the very reasonable levels as you can imagine
I think if an engine is leaking badly, oil and the “dirt” in it go bye-bye.
OTOH if the engine is burning oil that gets past the rings and/or valve guide seals those tight passages can act like a sieve and leave the dirt behind.
