Diesel retail is $5.967 a gallon, the top of its 30-day range

Diesel retail is $5.967 a gallon, the highest it has been in 30 days and the full top of its range. It is up 13.5 percent over the month. The pull is crude: WTI is $100.05, up 20.2 percent in 30 days and at 93 percent of its range, with Brent at $104.61 on the same climb. When crude runs like that, diesel follows, and it has. ULSD futures back it up at $4.768, up 10.8 percent and at 85 percent of their own range.

The spread is what you can price against. The gap between diesel retail and wholesale is $1.30 a gallon now, about 23 cents wider than a month ago. That street margin has widened in your favor even as replacement cost climbed. Gasoline has lagged the move, at $4.295 and only 81 percent of its range, up 3.7 percent, so the margin story right now is a diesel story, not a gasoline one.

The one to watch is the 3:2:1 crack spread, which is $54.06 and about $11 tighter than a month ago. The crack spread is the refiner's margin, and when it narrows this far while crude holds up, refiners have less reason to run hard. That could tighten diesel supply and push wholesale back up, which may squeeze the $1.30 you have now from the cost side. It is worth keeping an eye on your next few loads rather than assuming the wide spread holds.