Take it for what its worth ...
Heard some lady from the Petroleum Institute say that the reason that Diesel is so high is that the distillates used to create diesel are used in home heading oil and that since we are having a very cold winter (especially in the Northeast), this is the reason for the high prices as well as the Venezuela turmoil and some refineries being down for maintenance.
She said that every time there is some investigation into the "high fuel" prices, it is always determined that it was market forces at work and not some conspiracy ... and thats all.