Oil Leak

[Loie]

About 6 months ago, I discovered that my 1999 Corolla was burning oil. I have the oil changed every 3,000 miles pretty consistently, drive about 400-500 miles a week and have at present 169,000 miles. I had the car serviced 2 weeks ago and today it was bone dry. I have been checking regularly each week and for several months I need to put in about 6 quarts of oil between the 3,000 mile oil changes. There is no oil on the ground, no significant leaks visible in the engine, no blue smoke pouring out the back. I have a reliable mechanic who is mystified by the problem. I would be grateful for any clues to solve this mystery.
Thanks for any help or advice you can give!

[speedracer41]

are you using synthetic? it will burn off and you might not be able to tell.

[Loie]

Well, gosh, this is where I show my ignorance -- I haven't got a clue as to whether the oil is synthetic! I have had my car serviced by the same mechanic for years, and just recently by a new mechanic who is trying to figure out the problem. I would assume the same type of oil has been routinely used over the years, but I could be wrong. If I can be REALLY stupid, how do I tell if a synthetic oil has been used?

Thanks, Loie

[Brian R.]

If you paid $20-30 for the oil change, it is dino oil. If you paid $40-50 for the oil change, it is synthetic. Really, in general, mechanics use dino oil unless you tell them differently.

[asn13oy]

I swear, if I didn't have a haynes manual, I'd be no help at all in this forum.

The following are possible problems:
- Oil pan gasket and/or oil pan drain bolt washer leaking
- Oil pressure sending unit leaking
- Valve covers leaking
- Engine oil seals leaking
- oil pump housing leaking

[johnholl]

Originally Posted by asn13oy

I swear, if I didn't have a haynes manual, I'd be no help at all in this forum.

The following are possible problems:
- Oil pan gasket and/or oil pan drain bolt washer leaking
- Oil pressure sending unit leaking
- Valve covers leaking
- Engine oil seals leaking
- oil pump housing leaking

The Haynes manual is very useful. My wife's 1999 Prizm uses oil as well, my guess is internal consuption with a little leaking. Common with the 1.8L i think. Anyhow, it's not a great deal on our driving routine. 20miles per day [quart a month], but on long trips it's much much worse.