Crude Oil Definition

Crude oil can be defined as a mixture of naturally occurring hydrocarbons. Actually, crude oil is comprised of hydrocarbons, organic compounds and small amounts of metal. Crude oils are named according to their contents and origins, and classified according to their per unit weight (specific gravity). Heavier crudes yield more heat upon burning, but have lower API gravity and market price in comparison to light (or sweet) crudes. Crude oil has to be changed before it can be used for anything. This happens in an oil refinery where they are refined into diesel, gasoline, heating oil, jet fuel, kerosene, and literally thousands of other products called petrochemicals.

There are clear cut definitions for light and heavy crude oil based more on practical ground than theoretical. Now, let’s look at definition of light and heavy crude oil:

Light Crude oil Definition

There are variations in definition of light crude oil. These variations occurred because countries such as Canada and Mexico tend to have heavier crude oils than are commonly found in the United States, whose large oil fields historically produced lighter oils than are found in many other countries. New York Mercantile Exchange (NYMEX) defines light crude oil for domestic U.S. oil as having an API gravity between 37° API (840 kg/m³) and 42° API (816 kg/m³), while it defines light crude oil for non-U.S. oil as being between 32° API (865 kg/m³) and 42° API (816 kg/m³). 

The National Energy Board of Canada defines light crude oil as having a density less than 875.7 kg/m³ (30.1° API). The Mexican state oil company, Pemex, defines light crude oil as being between 27° API (893 kg/m³) and 38° API (835 kg/m³). 

Heavy Crude oil Definition

Heavy crude oil is crude oil that is highly viscous, and cannot easily flow under normal condition. It is referred to as "heavy" because its density or specific gravity is higher than that of light crude oil. Heavy crude oil has been defined as any liquid petroleum with an API gravity less than 20°. Physical properties that differ between heavy crude oils and lighter grades include higher viscosity and specific gravity, as well as heavier molecular composition.