A major research program has been undertaken to assess the diesel fuel requirements of a broad spectrum of diesel engines, primarily in terras of ignition quality. The fuel requirements of several light and heavy duty diesel engines have been evaluated in programs completed on the road and in a climate controlled chassis dynamometer. Diesel fuels of various qualities representative of current and projected production have been evaluated in these engines over the temperature range of −20 to 25°C. Engine performance has been rated in terms of cold startability, cold smoke, noise, power, fuel consumption and exhaust emissions. These evaluations are preliminary to a much larger program and further details will be published at a future date.