Mazut is a heavy, low quality fuel oil, used in generating plants and similar applications. In the United States and Western Europe, mazut is blended or broken down, with the end product being diesel. Mazut-100 is a fuel oil that is manufactured to GOST specifications, for example GOST 10585-99. Mazut 100-75 VLS and Mazut 100-99 Grade I are actually the same thing. GOST merged the old classifications of 75 and 99 into a new seven grade classification, all under 100-99. For whatever reason, many people still use the old 75 classification; particularly the Chinese.
