What does “Schweröl” mean in German?

Schweröl splits cleanly into schwer (heavy) + Öl (oil) — and the name earns its adjective. It is the dense, black residue left at the bottom of a refinery after lighter products like petrol and diesel have been extracted. At room temperature it barely moves, stretching like syrup; a cigarette lighter cannot ignite it. That cheapness and energy density is why the world’s cargo fleet runs on it.

The compound models a pattern German uses across industry: stack an adjective onto a material noun and you name a grade or type — Rohöl (crude oil), Leichtöl (light oil), Schwermetall (heavy metal). Once you spot schwer- as a prefix you can decode unfamiliar industrial terms on sight. In the clip the presenter holds up a clump of the substance at room temperature to show why ships must heat it hard — well over 100 °C before it will flow through the pipes and burn — a vivid demonstration that makes the “heavy” in the name impossible to forget.