Diesel's retail-wholesale spread is 1.384, its widest in the past 30 days

Diesel street margin is as wide as it has been all month. The retail-wholesale spread is 1.384 now, up 0.183 over the past 30 days, so a station is holding about 18 cents more per gallon over its cost than it was a month ago. Pump diesel at 5.652 is sitting at the top of its 30-day range and up 6.4 percent, while ULSD futures at 4.194 are down 4.0 percent and 79 percent of the way up their range. Retail moved up while the wholesale benchmark eased, and the extra margin came from that.

If you buy diesel and resell it, that spread is the number to price against right now. It could hold as long as retail stays firm and futures keep drifting, but a spread this wide tends to draw price competition on the street, so it may narrow if a nearby station cuts to move volume.

Gasoline is the other side of the board. RBOB is 3.009, down 11.4 percent over 30 days and only 25 percent up its range, near the low end. The 3:2:1 crack spread is 59.96, down 11.9 over the month, so the blended refining margin on a barrel is tighter than it was. Gasoline weakness is doing most of that work while diesel holds up.

Natural gas is quiet at the Henry Hub, 2.86 and up 5.0 percent, sitting 31 percent up its range. Storage is now 109.483, at the very top of its 30-day range and up 7.0 percent, so the build has been steady with no supply scare in the numbers.

The one thing worth watching is that diesel retail spread. It is stretched, and street margin this wide usually invites a competitor to undercut, so it looks set to face some downward pressure in the next week or two if wholesale stays soft.