The fuel injection system, the timing of fuel delivery into the engine and the quality of fuel used all contribute significantly to emission reduction. Correct diesel fuel-either 1-D, 2-D or winterized 2-D is to be used. Do not use heating fuel oil or diesel fuels intended for industrial or marine use. Buy fuel from a reputable dealer and avoid the use of additives. The diesel fuel system is discussed in detail in Fuel System of this repair guide.