Why am I using oil? 168000 miles oil changed reg. not smoking,new Pcv on 2003 Mazda Protege

Had car since new. Plugs are white with no oil residue. No leaks. New pcv valve.
Using 1 qt in less than 1000 miles. Not smoking. What could the problem be?

Asked by for the 2003 Mazda Protege
well its not uncommon for cars with this mileage to use approx 1/2 to 1 qt per 1000 miles. you could do a leak down test to ck rings in cyl's