Steel Frontier.

Set in a post-nuclear-holocaust future, this sci-fi western takes place in the frontier city of New Hope, the only place around with a working oil refinery. Ever since a megalomaniac general and his followers took over the place, life has been miserable. Then a stranger, a man-of-few-words, comes to town. A quick-drawing gunslinger, he first joins the conquerors. As time passes, however, it rapidly becomes apparent that he really sides with the townsfolk, and when the time is right, he leads them into a violent uprising.