However, as noted, successful treatments have been conducted on reservoirs with oil gravity as low as 16°API. The bottom limit of oil gravities where this process can be successfully applied is not yet known. The highest gravity oil to be treated is 41°API gravity oil in the Devonian sandstone in Alberta, Canada. Generally speaking, oil with an API gravity between 40 and 45° commands the highest prices. Above 45°, the molecular chains become shorter and less valuable to refineries. Crude oil is classified as light, medium, or heavy according to its measured API gravity. Light crude oil has an API gravity higher than 31.1° (i.e., less than 870 kg/m 3) The relative density of petroleum liquids can also be uncovered by using API gravity value: RD at 60 o F = 141.5 / (API gravity + 131.5) A key formula for establishing barrels of crude oil per metric ton. Using the following formula, API gravity can also be used to calculate how many barrels of crude oil can be produced per metric ton.