Toyota - Corolla :: 1996 - Burning Smell / Smoke - Oil Light Occasionally?

My mechanic cannot figure out what's wrong with my car My car is a manual trans 1996 Toyota Corolla with almost 154K miles. I had the oil changed two weeks ago (about 1000 miles with my commute), and at that time, I let my mechanic know that it's been losing oil and so check it over. At that time, he changed the oil, cleaned the engine, and added a dye to the oil to show up any leaks.

I took it in this past Thursday for him to locate the leaking, and the mechanic let me know that 1) It came in mostly dry (no oil), 2) there was no visible leaking except for a seepage around the oil pan, which he says could not account for the loss of 4 quarts of oil in two weeks, and 3) it's not burning it out in the exhaust system.

A bit of the history of the car. I got it when it was at 59K, used, and there were a number of things wrong with it that I didn't discover until later, such as that no maintenance had been done to it at all in the 60K someone else had owned it. It came to me needing a timing belt, brakes, and an engine and radiator flush (the radiator fluid was brown instead of green).

At one point at around 70K, as a stupid teenager, I did let it run dry. The oil light came on, I panicked, shut it off, dumped in two quarts (which brought it to full on the dipstick, which I thought was weird), and took it straight for an oil change, where they told me it was dry, which was odd, because I'd just put 2 quarts in it.

After that, there were no issues until it hit about 120K. At that point, I started smelling burning oil and there was smoke coming from under my hood, so I towed it to my mechanic at the time. He replaced the valve cover gasket, the rear main seal, and the head gasket (with engine block machining and all). That more or less cleared the problem up, but then I took it across the country on a 3K road trip, and it ended up accidentally running dry again. Oil light came on, I shut it off, dumped in oil, took it for a lube job.

Since that time, it's been occasionally throwing me an oil light when I go downhill (I figure that this is because it's low but not out, and the change in pitch reduces the pressure?). Each time it does this, I've shut it off, coasted to a stop, dumped in 2 quarts (which brings it to full on the stick), and gone on, berating myself. These times have become more frequent, however, even though I now check the oil regularly.

So before I endure the deserved lectures about being dumb, yes, I blame myself, but regardless of my lazy maintenance, it's becoming ridiculous. My car is now finding a way to lose a gallon of oil over the course of 1000 miles, with no discernible leak or consumption.

Also, why my oil light comes on when it's only 2 quarts down on the stick sometimes, and then sometimes goes almost dry without throwing the oil light? I just got it back with the oil topped up, more dye in the engine, and instead of going for 2 weeks, I'm going for 1 week to see if maybe he can catch it in the act of learning this magic trick of vanishing oil.