Data Desk

The $136 Margin: Diesel's Spread Over Crude Left Gasoline Behind

The gap between what crude costs and what diesel sells for has blown out, and gasoline did not come along for the ride. Here is how to read the spread, and what it quietly adds to every diesel-burning line in your operation.

Take what a gallon of diesel sells for at the pump, multiply by the 42 gallons in a barrel, and subtract the price of a barrel of West Texas Intermediate crude. In August 2026 that arithmetic left $136.0 a barrel: the portion of a barrel of diesel that is not crude oil. Run the same numbers for gasoline and the figure is $83.5. When the measured window opens in September 2023, the two spreads stood at $101.8 and $70.4: diesel carried a premium, but the two fuels lived in the same neighborhood. They no longer do. Both come out of the same barrel of oil, through the same refineries, into the same distribution system. One of them has been repriced.

A spread indicator, not a refinery income statement

The figure is a crack proxy, a rougher cousin of the crack spreads refiners actually trade: the EIA's retail on-highway diesel price converted to dollars per barrel at 42 gallons, minus the EIA's spot price for WTI crude. Because the retail price includes federal and state fuel taxes, terminal and trucking costs, and the retailer's margin, the level overstates what any refinery earns. This is a spread indicator, not a refinery profit and loss statement, and it should be read as one. But taxes and distribution costs move slowly. When a proxy built this way swings by tens of dollars a barrel inside a year, the swing is happening in the space between the crude market and the pump: refining margins, product inventories, trade flows, and the balance of supply and demand for the finished fuel itself.

Diesel's implied spread over WTI, August 2026: $136.0 per barrel. Up from $101.8 when the window opens in September 2023, and just off the July 2026 peak of $137.0. Gasoline's equivalent spread stands at $83.5.

Two fuels, one barrel, two stories

The path matters as much as the level. By March 2025 both spreads had compressed, gasoline to $60.9 a barrel and diesel to $79.0. Since then gasoline has recovered $22.6. Diesel has added $57.0, a rise of 72.2% in under a year and a half, touching $137.0 in July 2026, the peak of the window, before easing to $136.0 in August 2026. Measured across the full window the asymmetry is starker: diesel's spread has widened by $34.2 a barrel since September 2023 and gasoline's by $13.1. For every dollar gasoline's spread gained, diesel's gained $2.61. The entire net move in diesel, and then some, has arrived since March 2025.

Why diesel? Distillate is the industrial fuel. It moves trucks, trains, barges, tractors, and excavators, and it backs up the generator behind nearly every plant, so its demand tracks freight, construction, and field work rather than commuting. A refinery can tilt its yield toward distillate or toward gasoline only within limits set by its hardware and its crude slate; when demand for the two products diverges, the spreads do the adjusting, not the barrel. Whichever mix of causes you weight, refinery closures, export pull, thin distillate inventories, the print is the print: the market now pays far more to turn crude into diesel than into gasoline. For a fuel buyer the cause matters less than the consequence, because relief in crude does not automatically become relief at the diesel pump.

Crude is not the author of this move. West Texas Intermediate traded at $84.77/bbl as of Aug 11, 2026 in the EIA's spot series, and retail diesel stood at $5.45/gal as of Aug 17, 2026. Run the arithmetic on those two live prints and the spread comes to $144.3 a barrel, a figure this page recomputes on every data refresh rather than freezing at publication. That habit of checking both numbers is the point. Crude wanders; the spread trends. A buyer watching only the crude headline had no warning of what the spread was adding to the pump price, and no way to see that a falling crude chart and a rising fuel bill were both telling the truth.

Crude sets the floor under the diesel price. The spread decides how far above the floor you pay.

What the spread costs a diesel burner

Here is the identity that turns the spread into a cost number. The pump price is crude plus the spread, divided across 42 gallons. So the $57.0 a barrel of widening since March 2025 works out to $1.36 on every gallon: money the pump price now carries that it would not if the spread had simply held its March 2025 level while crude did exactly what it did. Consider an operation burning 24,000 gallons of diesel a year, a small delivery fleet plus yard tractors and a standby generator. The widening alone costs it $32,571 a year, an expense no crude hedge and no crude forecast would have flagged. Measure instead from the start of the window in September 2023 and the spread's growth adds $0.81 a gallon, $19,543 a year for the same fleet.

What to do with the number

Start with your surcharge formulas. Freight fuel surcharges keyed to the EIA's weekly retail diesel price pass this spread through automatically; formulas and internal cost models keyed to crude do not, and the gap between the two methods is precisely the spread this article has been measuring. If you quote delivered pricing off a crude-linked fuel assumption, you have been under-collecting since March 2025. If you pay surcharges, expect them to stay stubborn even through a crude selloff, because any relief has to travel through the spread before it reaches the pump, and the spread has been traveling the other way. Then re-quote everything with a diesel line in it, delivered product, yard operations, generator standby, off the actual pump price rather than a crude-derived estimate. The number on the invoice is what you pay; the spread is what tells you where that invoice is headed.

Put the actual pump price, not a crude-based estimate, into the unit cost calculator to see what fuel adds to every part you ship. Reprice your diesel exposure

Published 2026-08-18.