Let's face it: Greasepit is big and dumb, and he oozes oil. Pretty much this guy in a nutshell.
Greasepit only as one major power: He oozes oil constantly. He could get an honest job at an oil refinery, and end the country's dependence on Middle East oil all by himself. If he was so inclined to get an honest job. He seems to prefer the job of "Enforcer".
Greasepit's true orgin is unknown, but he was with Limburger and Karbunkle on Mars. According to the episode, "Once Upon A Time on Mars", it was Greasepit who launched the missle that caused the injuries to Throttle, Modo, and Vinnie. (The comic book has a different explaination, though.) It is unknown if he is even human, since no human known oozes oil. (Thus, the "alien" rating for race.)
His stength, stamina, and unarmed combat seem to work only with normal folk. When going up against the Biker Mice from Mars, however, all that power falls short.
Limburger pays him nothing for his services, but Greasepit is still a loyal to his employer.