What does API gravity test measure?

The API gravity test is a measurement that assesses the density of petroleum liquids relative to the density of water. Specifically, it indicates whether a petroleum product is classified as heavy or light. A higher API gravity value signifies a lighter petroleum product, which generally means that it has a lower density and is more valuable in terms of refining and market price. Conversely, a lower API gravity value indicates a heavier product, which often requires more processing.

This metric is crucial in the oil and gas industry because it helps determine how easily the crude oil can be processed and the type of products that can be expected from refining. Heavy oils, for example, usually yield less gasoline and more residuals, while lighter oils have a higher yield of valuable products like gasoline and jet fuel.

The other choices refer to different properties of petroleum products that are not related to the density measurement provided by API gravity. Temperature stability, viscosity, and oxidation rates are all important factors in petroleum processing and usage, but they are measured by different means. The focus of API gravity specifically highlights the weight characteristics of the liquid, making option A the correct choice.