Summary:
Off-Road diesel fuel is very similar, although not the same as on-road fuel. Its easy to pick out off road fuel because its dyed red to indicate that taxes have not been paid for road use. For an end user it is important to know what additives are in either fuel. Its usually necessary to be adding additives for gelling and sludge removal. Off-road does have the benefit of having higher sulfur content than on-road fuels, this is being continually reduced to improve emissions however its at the expensive of lubrication. All of these conditions can be corrected with the liberal use of fuel additives. You will be hard pressed to get a straight answer regarding off-road fuel out of any company, however no one seems to be reporting known adverse effects.