White powdery spray pattern across the top plastic cover on the engine indicates a leaking radiator cap, a common problem. My 2005 did it for a couple of years with no significant drop in the coolant level until I realized what it was. I always mistook it for salt or dirt spray under the hood. A new $14 radiator cap from the dealer fixed this. NAPA, Autozone and Advance Auto did not have one. The rubber seal in the cap hardens over time and won't seal good enough under pressure with a hot engine. I figured it out when I checked the oil shortly after a 700 mile trip at 80+ mph and found fresh green coolant mist everywhere under the hood!