Ceramic fiber products are not used as fuel additives. They are inorganic, non-metallic materials known for their heat resistance, thermal insulation, and sound absorption properties. Typically, they are used in high-temperature industrial applications for insulation purposes, such as in furnaces, kilns, and other heat-intensive processes. Fuel additives are substances added to fuel to improve its characteristics, such as combustion efficiency, and are usually chemical compounds like detergents or stabilizers. Ceramic fibers do not serve this purpose and are not chemically compatible with the functions of fuel additives.