Originally Posted by doctor j

Go to the auto parts store and buy a small tub of GOOP hand cleaner. It's a white gelatinous goop. Rub a dollop of it into and around the spot and let it stand for 5 minutes or so. Throw it into the wash.

The stuff cuts oil and grease from your hands (intended use), and it cuts road grease from under the flares in the wheel wells on my truck.