Still ok at 31 degrees but not flash. Classifications or...

Still ok at 31 degrees but not flash.
Classifications or gradesEdit
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.[4]

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/m3)
• Medium oil has an API gravity between 22.3 and 31.1° (i.e., 870 to 920 kg/m3)
• Heavy crude oil has an API gravity below 22.3° (i.e., 920 to 1000 kg/m3)
• Extra heavy oil has an API gravity below 10.0° (i.e., greater than 1000 kg/m3)

However, not all parties use the same grading.[5] The United States Geological Surveyuses slightly different ranges.[6]

Crude oil with API gravity less than 10° is referred to as extra heavy oil or bitumen. Bitumen derived from oil sands deposits in Alberta, Canada, has an API gravity of around 8°. It can be diluted with lighter hydrocarbons to produce diluted bitumen, which has an API gravity of less than 22.3°, or further "upgraded" to an API gravity of 31 to 33° as synthetic crude.[7]