Nissan Repair: High Oil Consumption-contd, combustion chambers, oil consumption

Question
I wrote earlier and you responded to a problem I am encountering with an almost new Nissan guzzling oil. I had in hand the service invoice stating the dealer service dept. had worked on the intake manifold, so I inquired how that might possibly create an oil use problem. Now the Service Manager says they never worked on the intake, rather they changed the manifold converter. Their record says "exhaust manifold (internal damage) replaced manifold converter." The engine code that was stored was P0420. Could a failed cat converter have led to high oil consumption? The dealership is insisting on an oil consumption test...bring back when 1 qt low for them to add oil and record. At first they said bring back at 1000 miles but they changed that since it was more than 1 quart low in less miles. Now they wan't it brought back at 1qt low a total of three times for them to add and record. They didn't want to count the last trip toward the test because when I could not find oil on the dipstick after driving 700 miles, I added 1 full qt. and brought back to them (at their request). They added .5 qt to bring to full. They say Nissan won't accept this since I added the quart! The one oil addition they do credit to the test showed they added 1.25 qts. after 913 miles. I do believe the rate of consumption varies or is worsening, because in the period Nissan didn't allow it used 1.5 qts in 700 miles. I will have it back to them soon and they say they have a new PCV valve to install to "see if that helps".  

Answer
John,

It sounds like you have ring problems and you should be rasing all kinds of heck with the dealer.  Ge the local zone representative involved now and call Nissan corporate too.  Get this problem addressed and have Nissan give you a new engine.  The only way a PCV is going to cause oil consumption is if the oil returns in the head have been blocked or the baffle is out of the valve cover and the engine is sucking engine oil into the combustion chambers.  So, I am going with rings.  The last time I saw an engine that was prefectly good and using oil was an old Mitsu that had a bad baffle in the valve cover.  The thing ate a quart of oil every five-hundred miles.  Replaced the valve cover and it corrected the problem.