Mazut a heavy low-quality fuel used in power generating plants and similar applications. In the U.S. and Western Europe, mazut is blended or broken down, with the final product that is diesel. The Mazut-100 is a fuel that is produced under the GOST specifications, for example GOST 10585-99. Mazut is almost exclusively manufactured in the Russian Federation, Kazakhstan, Azerbaijan and Turkmenistan. The most important thing is to qualify the fuel sulfur content. The VLS Mazut 100-75 and 100-99 Mazut Grade I are actually the same thing. GOST merged the old classifications of 75 and 99 in a new classification of seven degrees, all under 100-99. For some reason, many people still use the old adjective 75, particularly the Chinese.