Diesel's retail-wholesale spread is 52 cents wider than a month ago

The diesel retail-wholesale spread is 1.627 now, up 0.523 over the past 30 days. That is more than half a dollar a gallon of added room between what you pay at the rack and what you charge at the pump, built up over a month. If your diesel volume held steady, that widening is real margin kept on every gallon you moved.

The wholesale cost did not drop to get you there. U.S. diesel is 6.382, up 14.0% over the past 30 days, and it is at the 95 percent mark of its 30-day range, which ran from 3.459 to 6.529. Both ends moved up together, and the street price climbed faster than the rack. For a retailer, that is more margin than a month ago, and worth watching while it holds.

Refiners saw the opposite. Their 3:2:1 crack spread fell 8.21 over the past 30 days, down to 65.2. The margin on turning a barrel of crude into product got tighter even as the pump-to-rack gap got wider. The money this month is at the retail counter, not the refinery.

Gasoline is the one to watch. It is 4.603, up 9.4%, and at the 99 percent mark of its 30-day range (low 2.907, high 4.628), about as high as it has been in a month. That close to the top, it could give some back if crude eases, so a retail gasoline margin built on today's price may not hold as long as the diesel one.