My first thought is condensation, as atomarc says, especially if the weather is cool and humid. If water is leaking into the crankcase in any quantity, you should see high oil level after the engine stands for a while. But it all gets mixed up if you run the engine. If you have any doubts about water leaking into the oil, change the oil- engine cold. If you get more than a couple of drops or water when you loosen the drain plug, there may be something more going on. If the engine was warm when you drained the oil, save the old oil and see if water settles after a few hours. If that happens, you could have a water leak to deal with, maybe the head gasket. But don't get too excited without further reason.
Harvester
