I'm wondering why my '92 wagon is using up oil so quickly. There is no oil dripping in my driveway, and the sides of the engine don't indicate a leak.

I had an oil change 2.5 months at 190K miles. Only 2K miles later the low oil light comes on. Evans Tire did the change and used Valvoline 10W30, but the problem preceded that.

I bought the car from the original owner in May 2006. He had regular dealer service and I have all the receipts.

The head gasket was replaced at 97K.
There is nothing in the receipts about valve seals.

When I bought the car, the oil usage was not a problem; it started happening about a year later. So I'm wondering what to look for. One of the members said W124s are notorious for oil leaks.

There is no oil in the coolant. I would check the spark plugs but I can't get the damn things off and don't want to risk breaking anything.

The car has been running fine, no overheating, though from time to time the idle fluctuates a bit at stoplights.

I just added 1/2 a quart of 10W40 (I'd have added more, but I can't manually get the cap off). Should I try 20W50?

 

That sounds like mine and it's pretty normal. I need to change the timing cover gasket and i have to put a quart every 2k miles. Just use 20/50 and you shouldn't have to change it until about 3k miles. Also only fill it to the middle and never top it off because you can damage you oil pan gasket by overfilling. Also remember oil get way thinner with use so by the time the next oil change comes around you'll probably will start burning up more oil.