Bought an 02 Corolla. It runs great and has great gas mileage but uses a quart of oil every 500 miles. It doesn’t smoke at all and does not foul spark plugs. Where could the oil be going?
Have you checked for leaks??
First–have you carefully checked to determine if there is an oil leak?
Oil consumption could be due to a leak and/or actually burning of that oil. If the car is burning oil, the catalytic converter will conceal that situation for awhile, until the CC is so overburdened by the oil residue that it ceases to function. Then, you will have a really big expense to replace the CC, so it is best to determine the cause of this excessive oil consumption a.s.a.p.
How many miles on the odometer?
Did you obtain the car’s maintenance records? If not, then shame on you for buying what could have been an essentially un-maintained car.
If you did obtain its maintenance records–How often (on average) has the oil been changed?
If this car was subjected to excessively long oil change intervals, and/or it was ever run with a low oil level, and/or if it was ever overheated, there could be heavy internal wear, thus leading to excessive oil burning. The only way to remediate this internal wear would be to tear down the engine and overhaul it. Is the car’s book value sufficient to warrant that expense?
If you are VERY lucky, the problem could be the result of a clogged PCV valve. A gunked-up PCV valve can lead to both oil leaks and to oil consumption, so replacing this very cheap part right away should be at the top of your agenda. As well as replacing the PCV valve, it would be a very good idea to use solvent to clean the PCV hose as well.
After taking care of the PCV situation, you should do an oil change, and switch over to “high mileage” motor oil, which might reduce the rate of oil consumption. Then, after that oil change, monitor the oil level very carefully to determine if the rate of consumption has been reduced. If not, then do a careful check for leaks, and if that proves negative, then you will have to decide if the car’s book value warrants overhauling the engine.
If there are no external leaks then it’s burning the oil and the first step is a compression test.
These cars often do have excessive oil consumption issues due to sludging of their underdesigned oil galleys for their oil control rings. There is an improved piston design for the 1ZZ-FE that features more and larger oil galleys to prevent them from clogging up with sludge so easily. The solution is to rebuild the engine using these improved pistons. The alternative is to live with it and add oil as needed. Here is an image of the old design vs new. The improved design is on the left:
But first, as VCD suggested, have the PCV system serviced from end to end, not just the valve…Look for signs of oil in the air-intake path, from the air-filter box to the throttle body…If you find oil there, you have a PCV problem…
You might also want to check the oil pressure sending unit. Sometimes they crack allowing the oil to leak out.