Light, sweet crudes are cheaper to pump, transport, and distill and produce more gasoline per barrel than other types of crudes so it generally goes for more dollars per barrel than others.
Sweet light crude oil yields the most gallons of gasoline per barrel of oil and since it has low viscosity and low density, it is comparatively inexpensive to pump, transport, and refine.
"They've been upgrading the fan plants and the pump plants little by little, " said Pete Foley, an official with Transport Workers Union Local 100, which represents many bus and subway workers.