Why has the diesel retail-wholesale spread widened to 1.384 this month?

The diesel retail-wholesale spread is 1.384 now, up 0.183 over the past 30 days. The spread is the retailer's gross margin on a gallon, the gap between what the street charges and what the marketer pays at the rack. It widened over a month when most of the other product signals were pointing the other way, so the question is what pushed it and who is holding the extra margin now.

The first place to look is the wholesale leg itself. U.S. diesel is 5.652, up 6.4% over 30 days, and that 5.652 is also the 30-day high. So the cost side of the retailer's math went up, not down. A widening retail margin on a rising wholesale price means the street price rose faster than the rack, or held firm while the rack caught up. Retail diesel is sticky by habit. Truck-stop and cardlock prices move in bigger, slower steps than the daily wholesale number, and when wholesale climbs into a posted street price that was already set higher, the measured margin opens up for a while before it compresses again.

The refiner's side of the barrel tells a different story. The 3:2:1 crack spread is 57.41, down 10.71 over 30 days. So the blended margin a refiner earns turning crude into gasoline and diesel narrowed by a real amount in the same month the diesel product got more expensive. Those two facts only fit together when you look at what the crack is made of. The 3:2:1 weights gasoline at two parts to diesel's one, and RBOB gasoline is 2.909, down 12.6% over 30 days from a 30-day high of 3.761. Gasoline is the heavier weight in that calculation, and it fell hard enough to pull the blended margin down even as diesel rose. The refiner running a standard slate earned less on the combined barrel this month. The diesel cut got dearer, but the gasoline cut lost more than the diesel cut gained.

That split is most of the answer to where the margin is landing. It moved along the chain. The refiner's blended crack came down by 10.71 while the retailer's spread went up by 0.183. Less of the barrel's value is being captured at the refinery gate and more of it is being captured at the pump, at least on the diesel side. That is a normal rotation, not a sign of anything unusual. The retailer who held a firm street price into a rising rack is having a good month on diesel, earned by carrying the inventory and the price risk while wholesale climbed under them.

Supply cuts against the easy read. U.S. petroleum inventories are 428.815, up 4.2% over 30 days. More barrels in tank usually leans on price, yet diesel rose 6.4% anyway. The number I have is the aggregate, not the distillate line on its own, but a firming diesel price against a rising total inventory points the tightness at distillate rather than at crude or the whole complex. Gasoline down 12.6% fits that. It is late August, summer driving demand is fading out of gasoline, and diesel tends to firm ahead of harvest and the fall freight season. I am reading the seasonal piece off the price moves, not off a demand figure, so hold that one loosely.

The wire has one piece on this, an Oil Price analysis headlined on why diesel margin could send WTI back to $90. The argument there is that a strong diesel crack pulls refiners to run harder for crude, which supports the price of oil itself. That runs into my blended number, because the 3:2:1 crack fell this month. Both can be true at once. A diesel-only crack can be strong while the blended 3:2:1 is dragged down by gasoline, and the FXEmpire read is about the diesel cut in isolation. I would not lean on that headline to call crude back to $90. It is one analyst's forward case and the only forward claim in it belongs to the analyst, not to my data.

So the spread widened because diesel wholesale climbed 6.4% to a 30-day high while street prices moved slower, opening the gap. That happened as the refiner's blended crack narrowed by 10.71, so value rotated down the chain from the refinery gate toward the pump on the diesel side. Underneath both is a gasoline price falling 12.6% while distillate firms, more a seasonal shape than a shock. I am sure of the rotation and its direction. How long the retail margin holds I am not, because a sticky street price is the thing that compresses once wholesale stops rising, and 5.652 is already the month's high.

And that was just the data. See you tomorrow.