Increased production of U.S. domestic crude oil, particularly light sweet crude from tight oil formations in Texas and North Dakota, has been replacing imports of foreign light crude oil processed by U.S. Gulf Coast refineries. With Gulf Coast imports of heavier crude oil remaining steady, this shift in light crude supply from imports to domestic production has changed the average quality of crude oil imported into the U.S. Gulf Coast (PADD 3).

One of the primary characteristics that distinguishes different grades of crude oil is density, or how light or heavy the oil is. Crude oil density is typically measured as American Petroleum Institute (API) gravity, which is a scale expressing the specific gravity, or density, of liquid petroleum products in degrees; the higher the API gravity, the lighter the crude oil.

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