I had the first oil change at 6800. Then skipped oil change, but checked oil which never showed low. At 22300 miles (this car was then 7 months old), the accelerator came full on when I accelerated and immediately after that there was a clacking noise in the engine whenever I accelerated. (Model is manual transmission; I thought something had come loose when I stomped on the accelerator pedal to see whether that would reset accelerator. Clutch was in of course.) Took it to dealership (not my home one; different city). First they said no problem, weather mat had caused accelerator pedal to stick. Then I asked them about clacking. They said, only .5 qt oil in engine, though I had checked as full before 500 mile trip. No leaking I had seen, or oil smoke while traveling. They said, no visible leaks to them either. They did oil change, and came back with "metal shavings in oil." Could missing the 14K oil change have caused this, as long as I was checking oil and oil full before I began the 500 mile trip? Please advise.