Red diesel is ultra low sulfur diesel, dye is added to the same fuel that is made for consumer use, the dye is to indicate that it is not taxed and therefor for off road use only. manufacturers dont like it used in the trucks they sell because they cant verify that the fuel meets 100% of the requirements for ultra low 15ppm sulfur content. Plus have u seen they way off road diesel is stored at most farms? in an above ground tank in the cow pasture somewhere all rusted to hell and it takes a farmer a lot longer to use the fuel in the tank (when he isnt harvesting crops) than it does a gas station so fuel doesnt get replenished with new freash fuel very often, it has a lot more time to to be exposed to water and other contaminants as well as algae that will grow in diesel and is almost always found in off road diesel tanks. Thats why manufacturers dont want to warranty injectors and high pressure pumps when red diesel is used. I am no longer allowed by ford to turn down certain warranty claims for injectors because red diesel was used if the fuel filters are clean, if they are clogged with algae, sand, rust and water then we are supposed to turn the claim down. I ahte doing that to poeple and usually dont if they will let me change their fuel filters, to save their a$$es in the long run. Supposedly the diesel comes from the same tank at the refinery and when a truck is supposed to load up with off road diesel the dye is injected as the truck is being filled. So red dye diesel is ULSD it used to not be that way with LSD for those who dont believe it i can provide documentation from ford about it if anyone would like to read it.