Crude oil contains much more than just carbon and hydrogen; it also contains nitrogen, helium, and other gasses , as well as relatively small amounts of sulfur, heavy metals, and other impurities.

As defined by the U.S. Geological Survey (USGS), heavy oil is a type of crude oil characterized by an asphaltic, dense, viscous nature (similar to molasses), and its asphaltene (very large molecules ...

EIA: higher crude density drove part of U.S. crude oil output growth last year. Texas accounted for 57% of the total production of crude oil with an API gravity between 30.1 and 40.0 degrees in the ...