There is no chemical difference between on-road and off-road diesel fuels. On-road diesel, also known as clear diesel, can be purchased at the local gas station. Off-road diesel is dyed red and is sold through bulk distributors.
Off-road diesel, or red-dyed diesel, is used by companies and individuals with vehicles that do not operate on public roadways. Businesses can use off-road diesel to provide fuel for heat, power marine vessels, and operate portable or fixed power generators and other equipment.