Toyota Repair: 93 Corolla excessive oil consumption, excessive oil consumption, internal passages

Question
Hi
Have a 93 Corolla 1.8 liter. Uses about 2 quarts of oil every 500 miles; has 115,000 miles on it. The car runs great and is in excellent shape otherwise, never any other problems. Bought this car at 93000 miles. Used a little oil, but suddenly seems to be using a lot more. What's the best way to go about diagnosing the most likely cause? I can check compression etc. Are there any possible causes other than the usual - rings, valves etc.? like blocked internal passages or frozen/stuck rings such that an engine flushing might help? Thanks for any advice!

Answer
The oil can be consumed in two ways, either there is an external leak or an internal one, external leaks are very obvious and if there are none the other possibilities are that the oil isw used up by the engine either because of worn oil control rings or leaking valve stem seals, both of these conditions will cause blue smoke from the exhaust, leaking valve seals will normally show blue smoke on startups and then disappear, worn piston rings will produce blue smoke on acceleration, check for these conditions and check back with me.