mean with respect to sulfur and cetane rating?
It means that the sulfur level is approved for highway use and catalytic converters. Diesel #2 is heavier than #1. It also (usually) has lower Cetane and more heat energy per gallon than #1. #2 will tend to form wax crystals and gel at temperatures below 10 degrees F. Most winter fuels are a blend of #1 and #2, but when it gets really cold I add fuel conditioner to avoid clogging the fuel filter with wax crystals. > 5.
