I just found out that my car lost 3 (out of 4) quarts of engine oil on a 3000 mile Thanksgiving trip. The mechanic says there is no leak so it must be burning it. He also said there is no way to know exactly what’s wrong without doing about $2000 worth of work on the engine. The car is a 2000 Corolla with 108K miles. Is this a typical problem for a car of this age? Also does this sound like a reasonable ballpark repair price? Could I just keep topping off the oil every few days or something? I’m leery of getting anything major work done because I got caught in a perpetual repair cycle 4 years ago with my last car, which was why I bought this one to begin with. Any thoughts?
That’s a lot of oil to be burning w/o some visual clue i.e.: blue smoke from the exhaust. You might look under the car and see if there are any oil deposits on the undercarriage. It could be that the oil is leaking, or being blown out, at highway speeds. Thats not typical usage for just over a hundred thousand miles, unless you rarely, or never, change the oil and filter. There are a number of things that could cause an engine to suddenly begin to burn oil, but most can be diagnosed w/ a few simple tests, certainly not $2000 worth of work.
I’d do some close inspection and maybe try a different mech.
Channeling **Rick ** or GaryT… 
If you don’t see a leak, the oil is probably being burned. If this is indeed what’s happening, there are two primary avenues for oil to get into the combustion chambers:
-
Blowing past the rings.
-
Seeping around the valve guide seals.
Both are fixable, though fixing #2 is usually much cheaper than fixing #1.
If your mechanic can’t find the problem without first doing $2,000 worth of work, it is time to find a new mechanic. :rolleyes:
Looking at it, 3 quarts in 3,000 miles is high, but not quite in holy shit territory yet.
Here is the deal, there are only a few places the oil can go.
You can leak it.
You can pull it past the piston rings
You can suck it past the intake valve seals.
A visual inspection is often adequate for checking for leaks. If there have been leaks, and the engine is a mess, a UV dye can be added to the engine oil to diagnosis a leak.
For checking the health of the engine, and sealing of the rings a technician can pressurize the cylinders one by one and measure how much of the pressure leaks out and just where it is going. This is called a cylinder leak down test.
Off the top of my head, I can’t think of a direct test for valve seals. A vacuum gauge will give you some hints, and inspection of the spark plugs should give you a pretty good idea if they are trash. If one or two of the plugs are fouled, I would suspect the valve seals.
Definitely time for a new mechanic. Assuming that the oil really is being blown/sucked out and not just leaking out somewhere that the now-rapidly-losing-my-respect mechanic couldn’t find, does it have to be repaired? Could I just pour more in or would that eventually result in an unscheduled stop on the side of the freeway?
I had a truck that had a bad engine/oil problem. It was a beater and not worth fixing up with an engine overhaul, so I just kept putting more oil it it. One of the spark plugs kept fouling up causing that cylinder to not fire. Whenever I noticed that it was running rough I took the plug out, cleaned it off, put it back in and away I went. I probably could have kept doing this for years. It’s a bit of a pain but you can do it.
This doesn’t sound like bad rings-modern piston rings are good for 200K miles. The suddeness sugessts several bad valve guide seals-which a decent mechanic can replace for about $500 (tops). A compression test ($70) will answer the question-I’d get a new mechanic.
I can’t add anything other than to concur with ralph124c that it sounds like valve seals, and Rick’s suggestion to check the spark plugs. I don’t know that checking the vacuum pressure will offer anything definitive, but I guess it’s worth a shot. As far as the car running as-is, in my experience many older motorcars, and especially British cars drink oil as if they were two-stroke engines, and yet keep running until the suspension rusts out or (in the case of British cars) finally develop so many untraceable electrical faults in their Lucas-built electrical systems that the owner pushes them into a ditch and resigns himself to a life of hitchhiking and public transit.
Oh, and ditch the mechanic who is trying to grift you out of $2,000 of hard-earned money.
Stranger
While rings should be good for several hundreds of thousands of miles, they can wear out early.
Bad valve seals will not show up in a compression test. A compression test will tell you if the compression is good or not. A leak down test will tell you if the intake, or exhaust valve or the rings are leaking. It also will not tell you if the valve seals are leaking.