Oil Ocean Zone is the ninth Zone of Sonic Mania, which is based on Oil Ocean Zone from Sonic the Hedgehog 2.
Returning to the Zone from Mirage Saloon Zone, Act 1 is very similar to the original, retaining the massive sea of oil dumped from Dr. Eggman's refineries that the player will sink into and die if they stand around in it for too long, along with the slippery oil slides, fans, networks of balloon launchers, and steam vent platforms to ride around on. This time around, touching the oil while using a Fire Shield will ignite the oil, causing it to rapidly go up in a blazing inferno for a few seconds.
The entire Zone is set aflame in the transition from Act 1 to Act 2, and the oil refineries are now pumping out toxic fumes at full force. These fumes will eventually cloud up the screen, making it more difficult to see where the player is going. Should the fumes become too thick, the player will start losing Rings every second until they reach zero; however, the fumes cannot kill the player. To clear the toxic fumes, the player must pull down on hanging switches much like in Sandopolis Zone, though the fumes will return after a while. There are also jumpable oil waterfalls, giant submarines that the player can enter inside and explore, and Sol Badniks that will set the oil on fire when destroyed.
From v1.04 onwards, the Zone ends with the player boarding one of the giant submarines, only for it to suddenly fly out of the oil and set a course for Angel Island.
In Encore Mode, Oil Ocean Zone's foreground palettes don't change very much, but the background palettes have been changed significantly, making the Zone look like it is set during the day. The buildings in Act 1 also appear to be brighter.
References and Easter eggs