Oil slick

Oil slicks are puddles mixed with spilled oil that appear as uncommon obstacles in the Mario Kart games.

Famicom Grand Prix: F1 Race
Oil slicks make their first appearance in the Super Mario franchise in Famicom Grand Prix: F1 Race. Here, they appear whenever unnamed CPU opponents are crashed into twice, retiring their car for the remainder of the race and leaving the oil—colored the same as the car—spilled where they wrecked. In time trial races, they appear in various places and colors in most of the courses. If the player drives over one, they spin out twice, unlike with other obstacles that merely spin them out once. They do not affect CPU drivers.

Mario Kart series
In the Mario Kart series, oil slicks primarily appear on standard road tracks, such as the Mario Circuit courses from Super Mario Kart, and cause drivers to spin out when they run over them. They are rather small and often placed at the edge of the road. Players can also jump (using a Feather) or hop over them. They appear in all but the first Mario Circuit in Super Mario Kart.

Oil slicks return in Mario Kart Wii on, Mario Kart 7 on , Mario Kart 8 and its Nintendo Switch port on , and Mario Kart Tour on SNES Mario Circuit 2 and SNES Mario Circuit 3. In Bangkok Rush and DS Peach Gardens R/T, similar ink puddles appear in a section of the course where they are spat out by Inky Piranha Plants. Unlike normal oil slicks, these ink puddles cover the screen with ink, similar to Bloopers.

Oil slicks appear in version 1.1.0 of Mario Kart Live: Home Circuit. Unlike in previous Mario Kart games, when one is run over, it causes the oil to cover the screen and makes the kart hard to handle.

Mario & Luigi: Paper Jam
Oil slicks also appear in Mario & Luigi: Paper Jam in the missions Wait Up, Yoshi! and Fly Guy Flyby, though they merely slow down Mario, Luigi, and Paper Mario.