Some may wonder what the difference is between the Audi S4 and the Audi RS 4, and how can anyone discern one from the other? There are several design cues separating the two, some more apparent than others. Among the more obvious examples are the flared wheels wells (sculpted into the body work and not simply tacked-on parts), gorgeous 19-inch alloy wheels, dual oval exhaust pipes in place of the S4’s smaller quad tips, the hunched-down stance, and RS 4 badges on the trunk lid, rear door moldings, and upper grille. The front fenders and hood are constructed of lightweight aluminum, and a subtle spoiler has been incorporated into the rear body design. Overall, the doors and roof panel are the only exterior panels shared between the RS 4 and other A4 models.