Mazut is an especially heavy residual product of oil refining, less refined and more viscous than the fuel grades normally discussed for ships. Dense smoke during warm-up is more than a cosmetic quirk: the heating and handling plant must bring the fuel into a combustible state, so visible trouble suggests wider engineering difficulties. Its high sulphur content and low refinement make it environmentally poor fuel, but cost matters when fleets buy fuel in enormous volumes. Warships often used cheap residual fuels before modern refining made cleaner grades more accessible.
Notable Point · 0:00-6:58
Why Kuznetsov's funnel smoke points to mazut handling
Kuznetsov's famous smoke comes from heavy residual mazut, which requires extensive heating and preparation before it will burn properly.