Red diesel

Red diesel is a rebated fuel used for heating, electrical generators and agricultural vehicles that rarely use public highways. In comparison to regular "white" diesel used in road cars, the tax charged on this fuel is much lower. Typical uses include the construction, marine and agricultural industries. The fuel is dyed red to prevent general use and provide easy identification to law authorities suspecting illegal use. As well as the coloured dye, an invisible chemical 'tracer' is added so that even if the dye is removed, tests on a fuel sample will reveal it to be non-road legal.

Some illegal organisations & gangs use makeshift refineries that remove the red dye from the diesel so that it can be sold as regular diesel. This diesel usually contains far higher levels of sulphur due to the acids that are used to remove the dye. The term washed diesel is used to describe this illegal diesel that has had its dye removed.