99 corolla, 190K miles, burns 5qt oil in 1000 miles

Check and clean or replace the PCV. An engine flush might loosen up the oil control rings and a heavier grade oil might help a bit.

You can't always see smoke from an engine burning oil. Your engine is also working it's hardest when driving down the road, so may be leaking oil then and not just when sitting in a driveway. You can give it a "leakdown" test to check oil blowby on the rings if you really want to evaluate the engine. Or accept the fact that you have an engine with 190K miles on it, assuming no past rebuilds, that's not bad. If you use Seafoam, follow the instructions explicitly, if you put it in the crankcase then you need to do an oil change after the prescribed number of miles.

I did replace the PCV valve but it didnt help. There was oil leak into the spark plug chambers so I replaced the valve cover gasket and it no more leaks in there or anywhere outside of the engine. BTW, what is an engine flush? How do we do it? I do use 5W-30 oil which is the recommended one.