White smoke is the result of incomplete combustion and is generally associated with engine start-up at low ambient temperatures. This condition is more predominant on high-horsepower fixed-injection-timing engines because the fuel and combustion systems are optimized for maximum performance and for reliability and durability under high load operating conditions. These engines can have two or three cylinders that misfire or have incomplete combustion when the engine is started at low ambient temperatures. The fuel that is injected into the cylinders that are misfiring is exhausted into the atmosphere as unburned hydrocarbons which cool, condense, and appear as white smoke. As the cylinder temperature and subsequently the coolant temperature rise, the misfiring cylinders begin to sustain combustion which decreases the hydrocarbon level in the exhaust, resulting in less white smoke being produced. Since white smoke is a normal characteristic of high-horsepower heavy-duty diesel engines during start-up at low ambient temperatures, it is extremely important to determine if the level of white smoke is significantly higher than normal for a particular engine model before making any attempt to correct a complaint. This can be accomplished by comparing the level of white smoke from one unit to another which has the same chassis configuration and engine model.