I like using Awesome, you can get it at the dollar stores. It works great on bugs and road grim and black streaks. I usually just spray it on and let it sit a minute or two and then wash with a soft brush or sponge and stuff just comes right off. My wife even uses it around the house to clean grease off the stove or on my greasy clothes or even cleaning stains out of the crapet.
Awesome Products Inc