This paper describes a test program where up to eighteen diesel fuels of varying qualities were tested for cold performance in sixteen commercial diesel engines. In this study, cold performance was defined as the time to start, intensity and time of white smoke emissions after the cold start and engine knock, if present, after the cold start. Initial tests were run at -20°C with starting aids (such as block heat and/or ether use) and at -5°C with no starting aids. Subsequent tests were only run under the latter conditions, as this was found to be more discriminating regarding fuel quality effects.The diesel engines were chosen to represent the diversity of engine design in North America, Europe and the Far East. Both Direct and In-Direct Injection engines were tested as were naturally aspirated and turbocharged engines. Engine build dates varied from 1980 to 1989. This range covers most of the current diesel powered fleet in North America. The fuel matrix tested was sourced to cover the general range of commercial fuels in North America in terms of cetane number, volatility and viscosity. Ignition improver was included in a number of the fuels.Results of the test program showed that engine type and calibration was the major factor controlling cold performance. The most important fuel parameters influencing cold performance were, in order, cetane number and volatility. The use of an ignition improver to increase a fuel's cetane number, was found to be comparable to naturally derived cetane at the levels of cetane number boost examined.