 Existing petrol engines can be converted at low cost in to 100% LPG or dual fuel with LPG for achieving enhanced fuel efficiency and economy with drastically reduced emissions.Non-subsidy LPG prices are below the diesel or petrol prices in India in terms of heat content (heat content wise one kg of LPG is equal to 1.85 liters of LPG or 1.37 liters of diesel oil or 1.48 liters of petrol).Cheaper butane, a constituent of LPG (propane and butane mixture), can be directly mixed with petrol/gasoline for better use in vehicles.