water marks on road near car wheels

[trojan]

I have often noticed patches of wet on the road in the mornings near the car wheels which at first looks like oil but eventually dry out. This happens on a dry night usually with a heavy dew. I assume it is the dew slowly running off the bonnet/roof but was wondering why it does not quickly dry out.

 

[Leo]

It's likely the run off channels from the windscreen drain water to those locations. Also likely that it doesn't dry out as quickly as you might expect due to the grease and oils collected in the water on the way.