Basically, On Road Diesel Fuel is just that, ULSD. If you get caught running dyed red Off Road Diesel Fuel, the fine is very steep. But you probably will not find it at truck stops or gas stations, so you don't need to worry. You will find premium or supreme ULSD now and then. It will be a couple cetane points higher than regular diesel, and have gone through a couple more filterings, but that is it. Premium or supreme ULSD is not necessary for any diesel engine. So all you need is ULSD (Ultra Low Sulfur Diesel). In the winter months if you travel in the colder temperatures you will want to make sure it is a winter blend. The pumps should state that. And ULSD will run just fine in older diesels, contrary to what you might read!