Term applied to the differential between what a typical refined products mix would yield, and the value of crude. The common crack spread features a per bbl reference derived of 66.6% unleaded gasoline and 33.4% No. 2 oil. The resulting average is compared to the WTI number for the resulting “crack spread.” Crack spreads of 3:2:1 use three parts gasoline, two parts of distillate to one part of crude.