My Corolla now has 345K miles. From around 150K miles to around 300K miles, it used 1 qt between oil changes (every 6K miles), which I considered to be normal considering its mileage. At around 300K consumption jumped considerably. It now goes through a qt every 700 miles. I changed the plugs about 20K miles ago and they had about 120K miles on them. They looked normal (they had a light tan powdery haze to them) and the electrodes were still in good shape. I expected them to show signs of oil fouling, but they didn't. I also changed my PCV valve, which did nothing to slow consumption. The car doesn't smoke when started after being parked over night, nor do I see any smoke coming out of the tailpipe when I'm driving. I had car headlights behind me at night which really shows a smoking engine, but mine shows nothing. Question is, where is this oil going? Could it be going out the tailpipe without burning it? It could also be going out through another part of the PCV system, but it seems like I'd be able to see it somewhere. It also doesn't leak. The engine runs fine and I'm just going to keep driving it until something major goes, but I can't figure out where all of this oil is going.
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