Heavy crude oil is a type of crude oil with high density and viscosity, making it significantly thicker and more challenging to extract and refine compared to lighter oils. Characterized by low API gravity, typically less than 20°, heavy crude is dense and sticky, which complicates its extraction and transport. This type of oil often contains higher levels of sulfur, metals, and other impurities, which require advanced refining techniques to process effectively. Techniques such as steam-assisted gravity drainage (SAGD) or thermal enhanced oil recovery (EOR) are commonly used to facilitate extraction by reducing its viscosity and improving flow.