| The main difference is sulfur content. ULSD (Ultra Low Sulfur Diesel) is the current fuel being sold and is rated at a maximum of 15 ppm (parts per million). This fuel is mandatory for 2007 and later model year engines (not necessarily model year vehicles, long story there). Prior to that we used LSD (Low Sulfur Diesel) which is rated at a maximum 500 ppm. And of course there is off road diesel which is listed as 500+ and usually dyed red or blue. Recently we have seen off road diesel below 500 ppm so the old school approach of dyed fuel is always above 500 is no longer absolute but it is important to still note. |