The Nitrox Afterburner was a special form of the Nitrox, used to speed up at velocities exceeding the standard formula. It was only seen when Vert used it to catch up with Golorum in his second, but unexcapable test of the Racing Realms in "The Ultimate Race".
The Nitrox Afterburner was a special, white device containing a highly potent, blue colored-form of the standard Nitrox. When used, the user's car executes a jet-thrust wheely as a blue aura glows over it and the blue flames are emited from the back of the vehicle.
This form of Nitrox seems to be made through a very complicated process with chemicals, due to its limited use and supply. However, it seems to give speeds over the normal speed, thus its "Afterburner" effect it gives. The creation of the flameable and volital feul is a huge mystery as it was a gift from Tezla and nothing else is mentioned about its formula or reasons it had to be made. It could be though that Tezla made this feul as a "Last Resort", thus saving it for a special occassion it had to be needed.