How a crude grade is described
Each crude grade has its own density and sulfur content. Density is expressed as API gravity: the higher the number, the lighter the oil.
Sulfur decides whether a crude is sweet or sour. Crude with less than 0.5% sulfur is commonly called sweet, and crude with more is called sour. West Texas Intermediate is a well-known sweet benchmark.
| Class | API gravity |
|---|---|
| Light | Above 31.1° |
| Medium | 22.3° to 31.1° |
| Heavy | Below 22.3° |
| Extra heavy | Below 10.0° |
These classes are common, but not every party uses the same grading. The contract names the grade and its limits.
Why the assay matters
An assay is a laboratory analysis of a crude grade. It shows the oil's properties and the yields of products it gives when refined. A refinery uses the assay to decide whether a grade suits its units, so buyers ask for it early in a trade.
How a crude trade is handled
- The buyer names the grade or quality range, the quantity and the delivery window.
- The seller provides the assay and the origin documents.
- An independent inspector measures quality and quantity at loading.
- Delivery terms and the pricing basis are fixed in the contract.
Questions we are asked
Which crude grades can you offer?
Grades and origins change with supply. Tell us the grade or quality range your refinery needs.
How is crude oil priced?
Price is usually set against a published benchmark, such as WTI or Brent, plus or minus a differential agreed in the contract.
How do I make an inquiry?
Send the grade, quantity, destination and delivery window through our contact page.