Sweet light crude oil yields the most gallons of gasoline per barrel of oil and since it has low viscosity and low density, it is comparatively inexpensive to pump, transport, and refine.

FORBES: China's Not Going Green

World crude oil production has in some cases already peaked (sweet, light) while others (heavy, sour) it has yet to be will soon.

FORBES: China's Not Going Green

Light sweet crude is depleting quickly, and now the industry is going after heavy crude and tar sands and thermally enhanced oil.

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