Oil Slicks are hazards in Mario Kart Wii. Hence the name, they are just small spills of black oil. Oil Slicks are incredibly rare obstacles in the game, therefore they only appear in Mario Circuit 3. Driving over an Oil Slick will cause players to spin out and lose any Items they were currently wielding. However, on the bright side, Oil Slicks are usually easy to avoid since they are placed near the edges of roads and are small. One can simply hop over an Oil Slick to safely pass one or stay out of its way.