In this study, A conventional diesel engine is modified to work in the dual fuel mode with LPG as the primary fuel and diesel as the pilot fuel. Experiments have been conducted to obtain brake thermal efficiency, emissions and combustion parameters at various diesel substitutions and outputs. There is an increase in the brake thermal efficiency from 35% in the diesel mode to 37% in the dual fuel mode at full load due to a rise in the combustion rate. However, poor ignition leads to a drop in the brake thermal efficiency and increase in hydrocarbon and CO levels at low loads, particularly with high diesel substitutions. It is seen that the NOx levels reduce in the dual fuel mode with increase in diesel substitution up to an output of 60% of full load. It is also noticed that the smoke emission reduces from 1.3 Bosch smoke unit (BSU) to 0.5 BSU with the dual fuel mode at full load. There is an increase of about 2° crank angle in the ignition delay and decrease in the peak pressure under light load and high diesel substitution conditions. The heat release rate shows a significant increase at high outputs which lead to knock.