Violtoil, a semi-portmanteau of the words "violet" and "oil", is a colourful purple-ish substance with characteristics comparable to those of diesel fuel, in that it combusts when compressed. One important difference, however, is that the combustion process is combined with a micro-fission reaction, producing far more energy than would otherwise be possible. The substance was discovered in 1949 by Dr. Saleen Wongya, who combined conventional diesel with a very small concentration of 99.9% pure U-259, better known as Warpstone. This type of fuel is capable of doubling or tripling the energy output of any combustion engine, though these must be especially modified to deal with overheating and extreme pressures, necessitating the use of experimental alloys and complex cooling systems. Furthermore, this mixed reaction is strongly radioactive, and necessitates the use of the corresponding measures (such as lead shielding or anti-fissile-product exhaust filters).
Thought lost in the wake of the 1958 Black Valley Nuclear Accident, the secrets of violtoil were recovered by one of the region's infamous stalkers and sold to a less-than-reputable energy corporation. Production, storage or usage of violtoil is a federal crime, as it can be easily centrifuged to obtain Weapons-Grade Warpstone.