Guide · Markets
Crack Spreads Explained: How Oil Refiners Make Money
A crack spread is the gap between the price of crude oil and the fuels refined from it, and it is the margin that drives refiners' profits and share prices. Here is how the 3-2-1 spread is calculated, why it tripled to about $53 a barrel in October 2026, and why refiners can fall when oil does.
A refinery buys crude oil and sells gasoline, diesel, jet fuel and other products. Its profit depends less on whether oil is expensive or cheap than on the difference between what it pays for the crude and what it gets for the fuels. That difference is called the crack spread, after the cracking process that breaks heavy hydrocarbon molecules into lighter ones. When the spread is wide, refiners earn a fortune on every barrel; when it is narrow, they can lose money even with oil at a low price.
The most quoted version is the 3-2-1 crack spread. It assumes a refinery turns three barrels of crude into two barrels of gasoline and one of diesel, roughly the output of a typical US Gulf Coast plant. The calculation uses futures prices: take two times the price of a barrel of RBOB gasoline plus one barrel of ultra-low-sulphur diesel, subtract three barrels of WTI crude, and divide by three to get a margin per barrel. Gasoline and diesel futures on the New York Mercantile Exchange are quoted in dollars per gallon, so they are multiplied by 42, the number of gallons in a barrel, before the subtraction. Simpler versions exist, such as the 1-1 diesel crack, which compares one barrel of diesel with one barrel of crude.
The crack spread is an indicator, not a refiner's actual margin. Each company buys a different mix of crudes, often cheaper heavy or sour grades rather than WTI, runs plants with different yields, and pays its own costs for energy, labour and environmental credits. Valero reports a realised refining margin per barrel each quarter, and comparing it with the benchmark spread over the same months shows how much of the industry's conditions a given company is capturing. Still, the direction of the benchmark is what moves the whole group of stocks, because it tells investors whether next quarter's margins will be better or worse than the last.
2026 provides a real example of how far the spread can move. With the conflict involving Iran disrupting Gulf crude exports and refinery output, fuel prices rose faster than crude. Benzinga, citing market data, reported the 3-2-1 crack spread at about $53 a barrel on October 21, 2026, against about $23 a year earlier, after a peak near $70 on October 7; New York Harbor diesel cracks were above $100 a barrel in mid-October, according to a Bank of America report, and the AAA average US diesel price reached a record $6.53 a gallon on September 22. On October 22 Valero reported third-quarter net income of $6.8 billion, or $23.89 a share, six times its year-earlier profit, with a refining margin of $39.24 a barrel against $13.14. By October 21 PBF Energy was up 202.5% for the year, Marathon Petroleum 190.3% and Valero 164.9%.
That example also shows the trap. On October 27, 2026, WTI fell 1.8% to $99.90 on hopes for talks with Iran, and refiners had their worst day since April 2025: Valero lost 9.2% and HF Sinclair 8.8%. Cheaper crude lowers a refiner's input cost, but investors expected fuel prices to fall even faster if Gulf refineries and shipping recovered, which would narrow the spread. Refiners are therefore not a simple bet on oil. They do best when fuel is scarce relative to crude, for instance when refinery capacity is lost to outages, sanctions or war, or when demand for driving and flying is strong, and worst when new refining capacity arrives or demand weakens.
To follow the spread yourself, look at the front-month WTI, RBOB gasoline and ULSD (heating oil) futures, convert the two fuel prices into dollars per barrel and apply the 3-2-1 formula; several data providers publish the result daily. Watch it alongside weekly US inventory data from the Energy Information Administration, where distillate stocks below their five-year average have usually meant wider diesel cracks. Seasonality matters too: gasoline cracks tend to widen before the summer driving season and diesel cracks before winter. A wide spread that is already reflected in record profits is a different setup from a spread that is just starting to widen, and the October 27 sell-off is a reminder of how quickly a crowded refining trade can reprice.