I recently changed the oil in my 2001 Ford Windstar. When I removed the oil filler cap there was a light tan colored gunk on the cap. There was also quite a bit covering the inside of the valve covers. The antifreeze level seems to be holding reasonably steady. I to a lot of short trips with the car.

Is this reason for concern or is it just due to moisture getting in the oil due to short trips?

 

I would say with the colder weather and short trips, you're getting moisture build up in your engine, then it's mixing with the oil. I drive 8 miles one way for work. I normally make sure that I take my buggy on an extended trip over the week-end to get the engine up to internal operating temperature to evaporate the moisture out of the engine. Just make sure that you have a good operating PCV valve so that the moisture can get pulled out of the engine.