Sulfur content

Sulfur content is the share of sulfur in a crude oil or fuel, and it determines how much a refiner must remove before the fuel can be sold.

Sulfur occurs naturally in crude oil in varying amounts, and refiners must remove most of it before turning the oil into fuel, both because sulfur damages refinery equipment and because burning high-sulfur fuel releases pollutants that most jurisdictions now regulate closely. The more sulfur a crude oil contains, the more processing capacity a refinery needs to strip it out.

This is why sulfur content, stated as a share of the oil’s weight, is one of the two properties, alongside API gravity, that most determines how a crude oil is classified and priced. Low-sulfur oil is sweet crude and commands a premium where refining capacity for heavier oil is scarce; high-sulfur oil is sour crude and typically trades at a discount reflecting the extra refining cost.