Ultralow sulfur diesel ULSD is a cleanerburning diesel fuel that contains a maximum of 15 parts per million ppm of sulfur ULSD contains 97 less sulfur than lowsulfur diesel LSD which typically contains 500 ppm of sulfur The European Union began mandating the reduction of diesel sulfur content in 1993 and the United States started phasing in ULSD requirements for highway vehicles in 2006 It was developed to allow for the use of improved pollution control devices that reduce diesel emissions ULSD can significantly reduce emissions when used in combination with cleanerburning diesel engines and vehicles It may react with strong acids or strong oxidizing agents such as chlorates nitrates and peroxides You should avoid contact with heat sparks fire and oxidizing agents The appearance of ULSD should be clear and bright free from visible sediment and water