Use of water diesel emulsions in diesel engines has resulted in drastic reductions in NOx and smoke levels, while the thermal efficiency is also improved. The objective of this work is to evaluate the effects of using water diesel emulsion as the pilot fuel in a dual fuel engine with LPG as the primary fuel. Tests were conducted on a single cylinder constant speed DI diesel engine. An emulsion with a water to diesel ratio of 0.4:1 was used. Performance, HC, CO, NOx, smoke emissions and combustion parameters were obtained and compared with the case where pure diesel was used as the pilot fuel. At high loads, the brake thermal efficiency with the emulsion as the pilot fuel was better than that with diesel. NOx levels were drastically reduced. The already low smoke levels were reduced further with the emulsion. There was an adverse effect on HC and CO emissions. The maximum rate of pressure rise and peak pressure were also higher with the emulsion. The use of the emulsion was not advantageous at low loads. Copyright © 2001 Society of Automotive Engineers, Inc.