Diesel is near the top of its 30-day range while gasoline is near the bottom

ULSD diesel futures are 4.405, up 6.2 percent over the past 30 days. At 95 percent of the month's range, they sit just under the 4.48 high. Retail diesel is 5.454, up the same 6.2 percent and sitting at 91 percent of its range. If you buy diesel, you are restocking near the most expensive it has been in a month. Gasoline is the opposite: RBOB is 3.059, down 10.4 percent, at the 30 percent mark of its range. So the two fuels have split, and anyone hauling both is paying more for one and less for the other.

Your street margin on diesel has not moved with the price. The retail-wholesale diesel spread is 1.017, essentially flat: up only two-tenths of a cent over 30 days. You are paying more per gallon at the rack, charging more at the pump, and keeping about the same cents-per-gallon you kept a month ago. The higher price ties up more cash in each tank of inventory without widening what you make on it.

Refiner margin says the same thing from the other side. The 3:2:1 crack spread is 60.44, down 6.42 over 30 days. The refiner's cut per barrel has narrowed by more than six dollars even as the finished fuel got more expensive, which happens when crude runs up faster than the fuels made from it.

Watch diesel futures against the 4.48 high. They have been sitting near the top of the range, and if they break through, retail diesel could follow and push your restock cost higher again. Gasoline near the bottom of its range may give some room to hold pump prices there while diesel climbs.