Bad piston rings or cross-threaded spark plug?

[9394volvo850s]

Can't a clogged PCV system also cause oil burning?

FWIW I put 1/3 of a can of seafoam into the oil of my wife's VW, ran it at idle for 5 minutes, and it went from burning 1 quart/700 miles to 1 quart/1500 miles. But her compression was low - half were at 160 (good as new) and half were around 95 (!). I haven't checked the compression again but might after I do another round of seafoam treatment.

I might try that GM top engine treatment however.

Oh and my #4 cylinder was also the lowest on my test. I've heard from several others they had the same results. Not sure why.

My 93 had 0 compression in the #4 cyl. barely used any oil. but it got dirty after like 2K miles. like 15 mpg in the city 22 on the highway. i ended up jus putting a much lower mileage motor it last fall. back to gettin over 500 miles to a tank. the old motor is sitting in my garage never took it apart to see what the problem was.