Burning major oil, what should I do?

I recently (two months and 2K miles ago) noticed that my car went from using -1.5 qts every 3k to 3/4qt in 500 miles! I haven't noticed any other issues and I have no reason to believe that anything went wrong when I replaced the timing belt, tensioner, idlers, water pump, thermostat, etc. around 2K miles ago... but it still begs to ask, is there anything that I could have done to increase oil consumption during the maintenance?

I know I'm not leaking the oil (though there is some seepage of gaskets as typical with 105K) but it's got to be going somewhere (haven't seen blue smoke, just the typical grayish smoke under WOT).

I know how much a pain in the ass changing the spark plugs were, is a compression test the next step or is there something a little less intrusive I can check first?

And just to make the thread interesting... I've decided to switch from Rotel T6 5W-40 synthetic to Subaru OEM synthetic 5W-30 during my next oil change, think that'l help?

Thanks for your input.

I doubt changing your oil brands will help, considering you are moving from Rotella to Subaru. Losing 3-4 quarts every 500 miles indicates a major issue. If you have no leaks externally, you are burning it. I know this is not the answer you are looking for, but if it were me, I would be doing a compression test.

Burning oil usually indicates either a cam seal, blown turbo or ring/piston failure. I would start with a compression/leak down test and see...it sounds too major to be either I the first two and both of those are usually followed by the blue smoke...

Check your PCV valve. 2008 WRX had a TSB for it and I believe same engine configuration as 05 LGT. WRX PCV valve would freeze in cold weather. If the valve doesn't release the crankcase pressure then the oil will be pushed out through seals, gaskets, everywhere it can.

Thanks for the input guys.

Just to clarify, I'm using 0.75 qts every 500 miles, not 3 or 4 quarts (could be misunderstood based on how I typed it above, my apologies). This is an increase of about 66% from what I've seen in the past. According to Subaru, oil consumption less than 1quart per 1K miles is "normal".

I did replace the PCV valve at 60K and can do that just to make sure, it's cheap and easy. That being said, since I can't find any oil anywhere I'm guessing this isn't the cause.

I'm skeptical of compression test results (when I do the test, never had results that made sense). I called the stealership and they told me they charge $450 for a compression test At least if I decide to do this they'll install new plugs at the same cost.

I'm still on the stock turbo so it's possible (and hopefully most likely) that's the cause. What failure modes would I see if it's the turbo? Would checking the shaft for play (by removing the down pipe) tell me if this is the issue? I'll also see if I can get some help from a friend to confirm I'm not blowing blue smoke.

Not sure how I could tell if the cam seal is junk... any thoughts?

Hopefully I'll be spending money on a new turbo/stage 2 mods instead of making sure my car is functional...

Just a thought, if I was burning 'major oil' wouldn't I see residue on my back bumper? I haven't seen ANYTHING aside from normal dirt/dust...

Turbo bearings shot/toast

If the motor is dry (like no oil in the engine compartment, or any where else) then it is probably the turbo,

Originally Posted by robinlsb

Turbo bearings shot/toast

If the motor is dry (like no oil in the engine compartment, or any where else) then it is probably the turbo,

^This seems to be the case, how can I confirm this? Remove the down pipe and check for play? I think I recall seeing some oil residue when I took off the TMIC, I suppose this would also point to the turbo.

Hhhmmm... Going to have to think about what's the best turbo for my application (daily driver, occasional auto X / lapping day). I don't think this car will ever see more than stage 2...

Turbo is easy. Spin it up with a strong pull and then let your foot off the gas. The resulting vacuum in the top end and induction system will suck oil through the turbo seal and give you the bug fogger effect.

Originally Posted by Captain Ned

Turbo is easy. Spin it up with a strong pull and then let your foot off the gas. The resulting vacuum in the top end and induction system will suck oil through the turbo seal and give you the bug fogger effect.

Just to clarify, if I go WOT from say 2K to 6.5K and let off the throttle without shifting I should see a cloud of blue smoke in the mirror, if I don't it's not the turbo? Sorry for all the questions, just want to make sure I understand what's going on and what to look for.

Thanks again guys!

That's the general idea. It doesn't confirm turbo, but it does confirm top end (intake/turbo/valvetrain). Of those, turbo is usually your best bet. If you get the smokeshow, then it's time to check the IC for oil and give the turbine bearing a good feel. If they're OK (and a bit of oil in the IC is not abnormal) then it's most likely valve seals.

That said, if you're in the first stages of turbo seal degradation, the smoke will be tough to see. If you've got a car friend, best to have them ride behind and keep you posted on the phone as you do the test.

Originally Posted by Living Legacy

Just to clarify, if I go WOT from say 2K to 6.5K and let off the throttle without shifting I should see a cloud of blue smoke in the mirror, if I don't it's not the turbo? Sorry for all the questions, just want to make sure I understand what's going on and what to look for.

Thanks again guys!

If you do that and see smoke, that's the pistons sucking oil past the valve seals.

If you have blue smoke on start up in the morning, that's valve seals leaking over night.

You should find a good machine shop and talk with them.

I appreciate all of the info guys. I have yet to have someone follow me or watch me start the car (after a night of sitting there) with the intent of looking for blue smoke, as soon as I do I'll post up the results. Having never seen blue smoke of any kind I'm clueless as to what's happening...

These cars have been known to not burn the same amount of oil every week.

Keep an eye on the oil and top it off.