Thought it might be diesel. This is why it is important to put ALL the car details in the question.
It is most probably a leaky diesel injector. The fuel dribbles out and runs in to the sump, it is diesel you see in your oil, not water.
You will have to get the injectors pressure tested to find out which one(s) is/are leaking. Change the oil and filter, the diesel will have thinned it and it will not lubricate properly. Keep running it and you'll wreck the engine.
dag
November 2009