A crude assay is a detailed analysis report that characterizes the physical and chemical properties of a specific crude oil type, including density, sulfur content, viscosity, and yield potential for various refined products. These reports are essential for refiners to determine processing costs, product yields, and appropriate pricing for different crude oil grades.

Crude assays significantly impact crude oil pricing and trading decisions, as different crude qualities command different prices based on their refining characteristics. Light, sweet crude oils with low sulfur content typically trade at premiums to heavy, sour crude oils due to easier processing and higher valuable product yields. Traders use assay data to identify arbitrage opportunities between different crude grades.

Real-world example: West Texas Intermediate (WTI) crude assay shows 0.24% sulfur content and 39.6° API gravity, commanding a $5 premium over heavier Canadian crude with 3.2% sulfur content due to superior refining economics.