Diesel's street margin is down 28 cents a gallon from a month ago

The retail-wholesale diesel spread is 1.356 today, down 0.283 over the past 30 days. That is 28 cents of margin gone from every gallon you move, and it is the clearest number for anyone setting a price at the diesel island this week. The wholesale cost held up while your retail price did not keep pace, so the gap you live on got thinner.

Crude is the reason to keep an eye on the buy side. Brent is 112, up 12.8% over 30 days, and it is at the very top of its 30-day range, the 100 percent mark. WTI is 99.46, up 5.1% and 81 percent of the way up its own range. Gasoline went the other way. RBOB is 3.107, down 10.9%, and it is at 36 percent of its range. So the barrel got more expensive while the product refined off it got cheaper, and the 3:2:1 crack spread tightened to 53.62, down 18.63 over the month. Refiners are earning less per barrel than they were four weeks ago.

ULSD futures are 4.721, down 4.5% on the month but still 68 percent up their range, so the wholesale floor under your diesel buy has not fallen much even as crude climbed. Your cost is holding firm and your retail margin is the part giving way.

If crude holds near the top of its range, wholesale diesel could firm up from here and press that street spread tighter still, so the 1.356 is the figure worth checking first thing before you post a price.