Uses a lot of oil

I bought car used six years ago with 48,000 miles. It used one quart per 1,000 miles.
It has gone down over the miles and now at 200,000 it uses about one quart every 400 miles.
It also gets black pretty quickly after an oil change.
I have heard that some 2002 to 2005' four cylinders had "bad rings" in them. Recently the engine light came on and it is related to an 02 sensor. My mechanic tells me that it is a result of the oil consumption and that he will not replace the sensor as it will just go bad again. He advised to either keep putting in oil until something major goes bad (spins a bearing or some other catastrophic issue) or sell the vehicle. He advised using 10w-40 rather than the factory recommendation of the 5w-20 to slow down consumption.
I would like to keep the vehicle as it was expensive and other than excessive oil consumption is a good vehicle.
Oil is cheap and if it fouls plugs, I can replace them for $30.00.
Is there a predictable decline in this type situation? I just bought new tires so would like to get another couple of years out of the car and it is great in Minnesota winters.