Diesel is up 6.2% and near its 30-day high while gasoline fell 11%

Diesel and gasoline pulled apart this month. U.S. diesel is 5.454 a gallon, up 6.2% over the past 30 days and sitting at 91% of its range, near the top. Gasoline went the other way: RBOB is 3.016, down 11% and at just 26% of its range, near the bottom. Two fuels off the same barrel, moving in opposite directions.

That split shows up in the refiner's margin. The 3:2:1 crack spread is 60.41, down 8.92 over the month, because the gasoline leg of the crack lost ground as pump prices came off. Refiners are earning less per barrel than they were 30 days ago, and the weak gasoline side is why.

For anyone selling diesel at retail, the higher price is not padding your margin. The diesel retail-wholesale spread is 1.017, up just 0.002 over the whole month. That is 1.017 a gallon gross, essentially the same as it was a month ago. Diesel cost you more at the rack and you charged more at the pump, and the gap between the two barely moved. ULSD futures back this up at 4.329, also up about 5% and also at 91% of their range, so the strength is in the wholesale market, not something happening only at street level.

Natural gas storage is the other number worth a glance. It is at 104.974, up 12.3% and pinned at the very top of its 30-day range. Injection season is doing its job and there is no tightness in the ground right now.

Diesel is close enough to its 30-day high that any further push could start pinching resale margins if the rack keeps pace, so watch the wholesale-retail gap rather than the headline price over the next week.