Sour crude oil

Sour crude oil is crude oil containing a high amount of the impurity sulfur. It is common to find crude oil containing some impurities. When the total sulfur level in the oil is more than 0.5% the oil is called "sour".

The impurities need to be removed before this lower-quality crude can be refined into petrol, thereby increasing the cost of processing. This results in a higher-priced gasoline than that made from sweet crude oil.