I was topping my oil off, just changed do synthetic about 600 miles ago. Should I be worried about this?

 

no, its just that... condensation.

 

Actually, it is a good sign. It means the engine is properly "burning off" any water contamination in the oil.

 

That's good to know, Thanks guys!

 

 

I'm guessing it has something to do with the humidity here. Because I don't know how water would get in it.

 

Water doesn't get in there really, it happens when hot metal is cooled overnight. As the metal gets very cold, it creates a very thin "icy" layer. When heat from the crankcase is introduced, upon start up, it evaporates. Nothing to worry about, transmissions also experience this ... pretty much any where you have heat + cold metal = condensation.

Edit: If it is drenched or dripping wet, then I start to would worry.

 

My experience has been that if you see condesation on your oil cap, you are not running the engine long enough to evaporate the moisture out of the crankcase. Do you live close to your work? Or is this just a weekender, that doesn't see any sustained running. That used to happen to my sister's car when I was young. She would putt around town and then shut it off after about a mile or two and the cap would be all milky.

 

No worries about condensation in the oil cap, perfectly normal. If you go to change the oil and you get a 2-stage pour (water/antifreeze first, then oil), then you have a problem. FWIW, when I drain my catch can during winter, it looks like Yoo-Hoo (I've heard of others experiencing the same thing).