My son has a 2008 Sub Outback, 5 spd runs well, adds a quart of oil every 1000-1200 miles since it has 156,000 on it which for this year/model and oil consumption seems normal based on what you read.
The day before he goes to school brings it into shop has the CT emissions check and it passes, has the Connecticut shop change the oil. 4.5 qts 5w30, new Pennzoil filter based on what the receipt says. Next day leaves on his 800 mile drive to college. 350 miles into his journey CEL comes on steady, cruise control starts to flash and then CEL starts flashing. He pulls over and pops the hood, engine running rough, lurching all over, a little oil smoke coming from near cylinder 3 . He turns off engine check oil on and there is none!.
Gets car towed to New York shop they confirm no oil in crankcase to speak of, there is no obvious leak anywhere under the hood or around the car except what would be expected seepage from the years, nothing fresh. It sat for 5 days, no oil pool under car. Coolant level is fine, no oil/frothy mix in anything. Codes pulled as P0302, P0303, P0028. First two are miss fire and likely reason for flashing CEL, 028 is oil manifold, bank 2 which was likely due to low oil level
NY Shop says the engine likely blown but need to get into it to diagnose. I end up spending $500 and get it towed back to CT. My neighbor is a 30 yr car mechanic so we pull oil plug and about 1qt very dirty black oil comes out. Pull off filter and, lo an behold, its not a penzoil but a car quest, looks dirty and not very new TBH. Put some new oil in it, change the filter. Sounds bit better but still rocking. Pull the plugs and all look good except #3, has oil on it. Compression test show 1,2, & 4 within a few lbs of 175 PSI. #3 is at 70 PSI. This is bad..
Back to original CT oil change shop for them to take a look.
Car was running fine before it went into shop for a simple oil change, 350 miles later, miss firing, huge oil consumption w/ no leak (at least 3.5 quarts would show up somewhere one would think?) and compression numbers that suggest the engine needs a rebuild.
What is the likely scenario causing the missfire and no oil?? Shop didn't fill crankcase? Sticky valve pushing oil?. I think the codes and the dark oil are a symptom of the final issues but not the cause. What would cause the engine to all of a sudden consume close to 4 quarts of oil in 350 miles?