My car operates with a huge margin under its performance limitations; aircraft engines tend to operate at higher RPMs and closer to engineering tolerances. I have the luxury of drifting to the side of a road in a car, which my aircraft do not.
Come on Re-heat, I'm sure you were much more worried about the cost of all this vulcanic ash lying on your car. I would have been. It could have ruined your filters, glaced your pistons and what not. You know how much that would have cost you? I'm sure you went walking!
I bet it's pollen as someone politely suggested.