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Different qualities of diesel fuels have been tested in naturally aspirated IDI engines and turbocharged DI engines to determine the effect on exhaust emissions (NOx, CO, HC, PAH, particulates, sulfates and smoke) and combustion characteristics (heat release, ignition delay) under cold ambient conditions. Measurements were made during engine warm-up and under steady state operating conditions at ambient temperatures between -20°C and +20°C. The startability was tested down to -30°C. The results showed that the behaviour of the diesel engine is dependent on engine design, the lubricant used and the fuel properties. Low viscosity and good flow properties of the fuel are important for starting - more important than cetane number, for example. Fuel consumption and exhaust emissions at the beginning of the warm-up period increased considerably as the starting temperature was reduced.

A low ambient temperature increases wear and fuel consumption in vehicle engines. The startability of the engine and the start-up of lubrication are highly dependent on the type of engine oil (mineral, semisynthetic, synthetic), whereas fuel consumption depends more on the engine type and driving conditions. The research work in a special cold chamber equipped with a powerful cooling system has so far involved three gasoline engines and two diesel engines. One gasoline engine was also tested in combination with an all-mechanical transaxle. Tests were carried out within the temperature range of +20…−30 °C using different engine lubricants in order to evaluate both lubrication during the initial start-up and fuel consumption during a test period of 30 minutes. Engines were run under both constant and cyclic load. Effects of auxiliary electrical block and oil sump heaters were also studied.