You might not notice what color diesel fuel you are putting into your engine but both the Internal Revenue Service and the Environmental Protection Agency are paying close attention.
Undyed diesel fuel is taxed when it leaves the refinery, under Internal Revenue Service (IRS) requirements. Red dye is added to non-road diesel fuel before it leaves the terminal to indicate its non-tax status. So, if you are driving on the highway, your diesel fuel needs to be clear.
The Environmental Protection Agency (EPA) uses the presence or absence of red dye to indicate whether the fuel is for highway use (not dyed) or for non-road use (dyed) under its diesel regulations. Since 2006, highway diesel fuel has been ultra-low sulfur diesel.
In June 2006, the EPA reduced the allowable level of sulfur in highway diesel fuel to a maximum 15 parts per million (ppm) sulfur. Diesel fuel used by non-road engines, trains, and marine vessels is being phased in to follow the same standard and it will become mandatory June 1, 2010.
One of the methods for preventing diesel fuel from gelling is adding kerosene. The kerosene has less wax in it thereby reducing the clumping that happens when temperatures drop. The issue is that kerosene is dyed red. If you use this method, you must be prepared to defend yourself to Department of Transportation inspectors.
Some on-road vehicles can get away with using dyed diesel fuel on U.S. roadways. Those used by non-profit agencies (such as schools) and the government are permitted to because they do not pay taxes on fuel.
