Ammonia, mostly known as a nitrogen feedstock for agriculture or as a refrigerant, has been occasionally used in the past as fuel for internal combustion engines and fuel cells. Because it is a carbon-free substance and has high octane number there is currently a renewed interest for using ammonia as a fuel. The potential benefits and technical advantages of using ammonia as a sustainable fuel for power generation on vehicles are analyzed here based on some performance indicators including the system effectiveness, the driving range. fuel tank compactness and the cost of driving. The cooling effect of ammonia is another advantage and is included in the efficiency calculations. Cooling with ammonia represents up to 20% from the engine's power. being thus a valuable side benefit of ammonia's presence on-board allowing for downsizing of the engine cooling system and obtaining some air conditioning. If the cooling effect is taken into consideration, the system's effectiveness can be improved by similar to 11%. It is shown that a medium size hydrogen car converted to NH3 becomes more effective per driving range cost at CN$3.2/100 km and fuel tank compactness with 18 L/100 km with a cost of ammonia assumed to be CN$0.3/kg. (C) 2009 Elsevier B.V. All rights reserved.