The fuels burned in the internal-combustion engines used by the Navy must meet the specifica-tions prescribed by the Naval Sea Systems Command. Thus, the problem of selecting a fuel with the required properties is not your responsibility. Your primary responsibility is to follow the rules and regulations dealing with the proper use of fuels. You must strictly adhere to all prescribed safety precautions. You must also take every possible precaution to keep fuel as free as possible from impurities. Even though proper handling and use are your prime responsibilities with respect to fuel, knowing the characteristics of fuels will help you understand some of the problems in engine operation and maintenance. At the time of manufacture, fuels are generally clean and free from impurities. However, the processes of transferring, storing, and handling fuel tend to increase the danger of contamination with foreign materials, a condition that can interfere with engine performance. Sediment and water in fuel can cause engine wear, gumming, and corrosion in the fuel system. Foreign materials in fuel can also cause an engine to operate erratically with a loss in power. For these reasons, periodic inspection, cleaning, and maintenance of fuel handling and filtering equipment are necessary.

Because of the differences in the combustion processes and in the fuel systems of diesel and gasoline engines, the fuels for these engines must be refined to meet different requirements. In general, diesel engines require a particularly clean fuel; otherwise, the closely fitted parts of the in-jection equipment will wear rapidly and the small passages that create the fuel spray within the cylinders will become clogged. The diesel fuel must have a composition that permits it to be injected into the cylinders in a fine mist or fog. Diesel fuel must also have ignition qualities that permit the fuel to ignite properly and burn rapidly when it is injected into the cylinders.