1. Crude oil characterisation

7. Crude Oil Assay Gravity, API o (specific gravity) Sulphur content
A Crude assay is a sheet summarizing the properties of a particular crude, including:
Gravity, API o (specific gravity)
Sulphur content
Pour Point
Carbon Residue
Salt content
Characterization factor
Aniline point
Nitrogen Content
Metal content
These give some indication as to how easy it is to process the oil, and may play a minor role in pricing.

8. Gravity of crude oil
Either American Petroleum Institute degrees (0API) or specific gravity (SG) provides information on the paraffinic or aromatic nature of crude. The API gravity of most crude oil falls between the range of 2O0API to 450API.
API (American Petroleum Institute) A trade association of firms engaged in all aspects of the U .S. petroleum industry including producers, refiners, marketers, and transporters.

14. Sulfur Content
High-sulfur crudes, especially those with a sulfur content >0.5 wt%, complicate refining and are also more expensive to refine. Sulfur and some sulfur compounds are corrosive toward metals and can decrease the pH of the crude oil. The sulfur content of most crude oil varies from <0.1% to >5%.
The terms "sweet" and "sour" are often used to characterize crude oils. These terms were originally coined to identify the characteristic hydrogen sulfide odor of the crude oil. They are now commonly used to distinguish the crude oil sulfur level. In general, those crudes containing approximately 0.5 wt% sulfur or less are considered sweet, and those containing greater than 0.5 wt% sulfur are considered "sour."

15. Universal Oil Products (UOP)