Sour crude is high in sulfur. Sweet crude is low in sulfur.

Petroleum is considered "sweet" if it contains less than 0.5% sulphur. Sour crude oil has >0.5% sulphur. Sweet crude oil also contains small amounts of hydrogen sulfide (H2S) and carbon dioxide (CO2).

Brent crude is extracted from the North Sea, and comprises Brent Blend, Forties Blend, Oseberg and Ekofisk crudes. Brent crude oil is usually considered as sweet crude.

Brent Crude is a light oil and is classified as a sweet crude. It contains 0.37% sulfur, has an API gravity of 38.06, and a specific gravity of .835.

This terminology depends on the sulfur content of the crude oil. Sweet crude oil contains less than 5% of sulfur, while sour contains over 5%/. In the nineteenth century, the oil would be tasted to determine its composition, and the lower sulfur content is reported to give it a slightly sweet taste and pleasant smell.

The Arabian Peninsula oil will be largely depleted of sweet crude by 2020