RomRaider

Hey guys, I've been loosing oil since my last 2 oil changes and wanted some opinions, I've got the trans outa the car right now for the next 3 weeks or so this would be the perfect time to try to figure this out.

Since my last two oil changes, I seem to be loosing about a qt in between each change (3k miles). Cant find any leaks anywhere. No oil in coolant. No oil on plugs, Piston caps look dry through the plug holes, no oil in turbo. Getting puffs of black smoke in between shifts and during rev's but I haven't seen any blue.

Did a compression test, both psgr side cylinders are at 130psi, drivers side cylinder closest to the cab is 130psi also, and the last one furthest from cab drives side is about 125 but it has a hard time getting there, gets about 120psi then takes a few more cranks to get to 125psi.

The manual says compression should be between 142psi and 171psi with no more than a 7psi difference between cylinders.

Also I've been getting a lot of random pinging. That I cant pin point to a specific area and doesn't seem to want to go away no matter how much I retard timing in the spots it pings. (This could be totally un-related though as I didn't log the car before having this issue).

Any opinions or ideas? Thanks.

BTW - This is a 2006 wrx.

do a leakdown test on all 4 cylinders. it eliminates some variables associated with running a compression test.

if #2 (driver's side front) comes out with high leakage i'd say you have a toasted piston.

What kind of oil are you using? Conventional or synthetic? What viscosity grade?

Is your car stock or modified? If modded, what kind of boost numbers are you running?

Running Mobile1 10w30 full synthetic since the first oil change.
Running about 18lbs of boost on a 20g.

I use straight 30 weight in the summer, it helps with consumption but doesn't eliminate it.

I've heard "some" oil use is "normal" on these engines, and the more boost you run the more blow by to expect. But in the end how much oil use is acceptable comes down to personal preference.

My car consumes about the same. (Sti 05) This is normal in our engines.

What about the compression?

130 / 130 / 130 / 125

Is that normal to expect at 50k miles with oil changes every 3k... It seems pretty far below what the service manual suggests. (142psi-171psi) - I'm putting together a leak down tester built as described Here and will try things out with that later this week.

ultimate pressure levels are not nearly the concern as balance amongst/across cylinders. this is because a mechanical issue that caused the same exact loss in all 4 cylinders would be extraordinarily unlikely.

i would try a different brand of oil.

i've had bad luck with mobil 1. i personally think it's a bad oil for our motors. try some syntec or penzoil platinum and see if anything changes. i use 10-40 in the summer and 10-30 in the winter and haven't had any issues. at around 70k miles, my car started to consume maybe 1/2 quart every 5000 miles. i was also pushing 25+ psi on a 16g, so i guess that's to be expected.....

Thanks guys, I think I will leave it alone for now and try a different brand of oil. What's your oppinions on Royal Purple?

Mobil 1 always went through like 1 quart or so on my subies. Castrol seems to stay until 3k.