So to buy the spreads, sell the crude, Buy the products. To sell the spread buy the crude, sell the products. Costs will vary according to crude type, and seasonal demands for the end product will have some effect on the spread. What's left is asphalt on the heavy end and butane on the light. Some traders like trading the Crude with one month forward on the product contracts to factor in the storage.
Most firms have considerably lower margin costs for spreads.