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Not all oils are the same


It’s quite often assumed that all oil is the same. Sure, some are heavy, while others are considered light. But what accounts for the difference…and does it matter?

Known as API gravity and derived from the American Petroleum Institute formulation, oil’s API gravity is one of the main characteristics of crude oil used by refiners when assessing different crude streams for refining into diverse petroleum products such as gasoline, diesel or even jet fuel.

API is calculated as the inverse of the density of a petroleum liquid relative to water, or a measure of the weight of petroleum liquid compared to water.  The higher the API gravity, the lower the density of the petroleum liquid, meaning light oils, like the ones found in North Dakota’s Bakken have high API gravities. The benchmark for high API gravity begins at 40.1 and so crude extracted from say, the Canadian Oil Sands, has an API of between 6-18 degrees while plays in the Texas Eagle Ford and neighboring Permian Basin, range at the higher lighter end at between 30 to 50 degrees API.

The numbers help explain why a continental supply of oils with varying API’s allows all refineries, and thus consumers, to benefit from differing oils. While Canadian heavy oil makes up nearly 70% of its total oil slates, the opposite is true in the U.S. where much of the oil and growth in output is light, representing 55% of all American output. On both sides of the border, both Canada and the U.S are expected to accelerate their predominant oil slates, furnishing flexible alternatives to waiting refineries throughout North America.

Little wonder then that the advantage of having different streams of heavy and light oils is both beneficial and a matter of good fortune for end users who may draw from the best both countries can offer. It also clearly helps better understand why the symbiotic relationship in energy is so vital to each’s respective prosperity.

Senior Petroleum Analyst, Canada

Dan is a skilled and noted bilingual (French and English) consumer advocate specializing in energy and current affairs. Known as Canada's “Gas Guru,” he founded to better help motorists anticipate the price of gasoline in advance across Canada. He has over three decades of experience in the petroleum industry, as a parliamentarian and an analyst.