I had to do an "emergency" oil change Sunday when it was 9* outside. All seemed to go as usual, except this time my hands were so cold that I dropped the filter and made a mess in the driveway. Anyway, now whenever I shut the engine off, I can hear a liquid (presumably the oil) draining somewhere (presumably into the oil pan). It sounds just like someone peeing into a toilet. No oil leaking that I can detect--there are some drips, but that is more due to my fumbling with the filter and getting oil all over everything in the area of the filter. What could be causing the draining noise? Maybe it's normal and I just never noticed this before?