Kerosene or diesel fuel usually works also, DO NOT USE GASOLINE, it works but it is dangerous to use due to its flammability. Most grease and tar removers will work in most cases. You will have to rewax the area, because whatever you use will also remove all the wax. If it has been on there for 2 years, then you might have trouble getting it off, because it has been set by heat cycles.
03 Silverado cclb 3500 drw, D/A, Reese 22k hitch
07 Alfa SeeYa Gold 30RL,2 slides,power everything