Alternative compression ignition engine fuels are of interest both to reduce emissions and to reduce U.S. petroleum fuel demand. A Malaysian Fischer-Tropsch gas-to-liquid fuel was compared with California #2 diesel by characterizing emissions from over the road Class 8 tractors with Caterpillar 3176 engines, using a chassis dynamometer and full scale dilution tunnel. The 5-Mile route was employed as the test schedule, with a test weight of 42,000 lb. Levels of oxides of nitrogen (NOx) were reduced by an average of 12% and particulate matter (PM) by 25% for the Fischer-Tropsch fuel over the California diesel fuel. Another distillate fuel produced catalytically from Fischer-Tropsch products originally derived from natural gas by Mossgas was also compared with 49-state #2 diesel by characterizing emissions from Detroit Diesel 6V-92 powered transit buses, three of them equipped with catalytic converters and rebuilt engines, and three without. The CBD cycle was employed as the test schedule, with a test weight of 33,050 lb. For those buses with catalytic converters and rebuilt engines, NOx was reduced by 8% and PM was reduced by 31% on average, while for those buses without, NOx was reduced by 5% and PM was reduced by 20% on average. It is concluded that advanced compression ignition fuels from non-petroleum sources can offer environmental advantages in typical line haul and city transit applications.