I have seen many post detailing issues with Hyundai Sonata engines consuming oil. Mine was solved simply by replacing the PCV valve at 100,000 miles. Upon discovering it a full quart low after never experiencing any noticeable problem, I monitored the consumption carefully and measure an increasing and very alarming oil consumption rate in excess of 1 quart per every 1,000 miles. I spent money on engine flush products thinking it was sludge causing oil to blow past the rings. I finally decided to change the PCV valve and problem solved. My theory is that the valve spring exceeded its fatigue life and opened to easily causing oil vapors to be excessively expelled through the valve into the combustion chamber and out the exhaust. The valve is only supposed to open when engine pressure gets close to exceeding a value that could blow out seals and gaskets then closes. It also opens to expel any moisture vapors that build up in the oil
due to condensation. If it opens too easily oil vapors are constantly expelled. I'd like to know what others think.