What is light sweet crude. Here is an excerpt from Wikipedia which might help:

"Classifications or grades [edit]

Generally speaking, oil with an API gravity between 40 and 45 commands the highest prices. Above 45 degrees the molecular chains become shorter and less valuable to refineries.^[1]

Crude oil is classified as light, medium or heavy, according to its measured API gravity.

• Light crude oil is defined as having an API gravity higher than 31.1 °API (less than 870 kg/m³)


• Medium oil is defined as having an API gravity between 22.3 °API and 31.1 °API (870 to 920 kg/m³)


• Heavy crude oil is defined as having an API gravity below 22.3 °API (920 to 1000 kg/m³)


• Extra heavy oil is defined with API gravity below 10.0 °API (greater than 1000 kg/m³)

Not all parties use the same grading.^[2] The United States Geological Survey uses slightly different definitions.^[3]

Crude oil with API gravity less than 10 °API is referred to as extra heavy oil or bitumen. Bitumen derived from the oil sands deposits in the Alberta, Canada area has an API gravity of around 8 °API. It can be diluted with lighter hydrocarbons to produce diluted bitumen, having an API gravity of lower than 22.3 API, or further "upgraded" to an API gravity of 31 °API to 33 °API as synthetic crude.^[4]"

^{Oiljob ... keep that ligth sweet crude coming.}

^{P.S.: If the gravity is less than 10 then the water will actually float on the oil.}