How Is Diesel Fuel Made From Crude Oil?

What crude oil brings to the refinery

Crude oil is a mixture of hydrocarbons, molecules of carbon and hydrogen, along with compounds of sulfur, nitrogen and oxygen. No two crudes are quite the same: some are light and some heavy, some carry more sulfur than others. That matters, because the crude a refinery runs shapes what comes out of it.

Refiners don't make a fixed recipe. EIA notes they adjust product yields in response to prices and market conditions by varying refinery processes and the types of crude oil they choose to refine. When diesel pays better than gasoline, a refinery can lean its units toward diesel, within limits.

How diesel is made from crude oil, step by step

EIA describes three basic steps every refinery follows: separation, conversion and treatment. For diesel, add blending at the end, then the trip to the terminal.

1. Distillation (separation). Crude is piped through hot furnaces, and the liquids and vapors go into distillation units. Fractions separate by boiling point: heavy ones at the bottom, light ones such as gasoline at the top. Diesel comes off in between. For #2 diesel, 90% of the fuel has to boil off between 540°F and 640°F.
2. Cracking (conversion). Distillation alone leaves a lot of heavy oil. Cracking uses heat, pressure, catalysts and sometimes hydrogen to break heavy molecules into lighter ones. A hydrocracker takes gas oil, which is heavier and boils higher than diesel, and cracks it into distillate and gasoline in the presence of hydrogen and a catalyst. EIA calls hydrocracking an important source of diesel and jet fuel.
3. Hydrotreating (treatment). The diesel stream is treated with hydrogen over a catalyst. The sulfur reacts with the hydrogen to form hydrogen sulfide gas, which is removed and treated to recover the sulfur. What's left can be brought under 15 ppm sulfur, the ultra-low sulfur diesel (ULSD) standard.
4. Blending. Refinery technicians combine streams from different units to hit the specification. For diesel under ASTM D975 that means properties such as cetane (a minimum of 40 for both #1 and #2), distillation range, flash point and lubricity.
5. Shipping to terminals. Most diesel moves by pipeline from refineries and ports to terminals near the places that use it, with barges and trains carrying some. Products share pipelines in batches, so diesel is tested to make sure it still meets spec. Trucks take it from the terminals to retail stations and large-volume users.

How much diesel comes from a barrel of crude oil

EIA puts the average at about 11 to 13 gallons of distillate fuel oil from each 42-gallon barrel of crude, most of it sold as diesel. In 2023, U.S. refineries produced 12.47 gallons of distillate per barrel, about 30% of the crude by volume. Gasoline is still the biggest product.

Source: U.S. EIA, Refining crude oil: inputs and outputs (Petroleum Supply Monthly, preliminary 2023 data). "Other products" is the sum of EIA's remaining categories; rows don't add exactly to the total because of rounding. Yields shift month to month.

Why 42 gallons in makes 44.65 out. Refining breaks big, dense molecules into smaller, lighter ones, which take up more space. EIA counts the difference as processing gain: 2.65 gallons per barrel in 2023, about 6.3%.

Where U.S. diesel comes from. U.S. refineries produce most of the diesel the country uses. In 2025 they made about 73.8 billion gallons of ULSD, against about 59.6 billion gallons consumed and 16.8 billion exported. Imports were about 2.4 billion gallons, roughly 4% of consumption, and about 84% of them came from Canada (EIA).

Ultra-low sulfur diesel: what hydrotreating gets you

Hydrotreating is why diesel today is ultra-low sulfur diesel. EPA began phasing in the 15 ppm limit in 2006. ULSD was phased in for on-road diesel from 2006 to 2010, and for nonroad, locomotive and marine diesel from 2007 to 2014, so dyed off-road fuel is ULSD too, apart from some exceptions for older locomotive and marine engines.

The side effect is lubricity. When refiners started deep desulfurization, they found that any significant cut in sulfur also cut the fuel's natural lubricity. In 2005, ASTM added a lubricity limit to D975: a maximum wear scar of 520 microns on the HFRR test. Lubricity additive is often injected downstream of the refinery, before the fuel is sold to wholesalers, because refiners generally can't add it before pipeline shipment: jet fuel moves in the same lines (Fuel Oil News).

One refinery, several diesels

• #1 and #2 diesel. #1 is the lighter cut, close to kerosene, with less wax for cold weather. #2 is the everyday grade with more energy per gallon. See #1 vs #2 diesel and diesel fuel grades explained.
• Clear and dyed. Off-road diesel is the same ULSD with red dye added to mark it for tax-exempt, off-highway use only. See dyed vs. clear diesel and what color diesel is.
• Weight. The crude and the refinery both change how much a gallon weighs. See how much diesel weighs per gallon.

How renewable diesel is made differently

Renewable diesel skips the crude. It's made from fats and oils using a hydrogenation (hydrotreating) process, the same family of chemistry a refinery uses to strip sulfur, though it takes more hydrogen than diesel desulfurization does. The result is a hydrocarbon chemically equivalent to petroleum diesel that meets ASTM D975 (EIA).

Biodiesel is different: it's made by transesterification of vegetable oils and animal fats, so it isn't the same molecule as petroleum diesel. That's why you see biodiesel as blends such as B5 or B20, while renewable diesel such as R99 is about 99% renewable. More in biodiesel vs. diesel and red diesel vs. green diesel.

From refinery to price per gallon

Every step above shows up in what you pay. EIA's breakdown of the retail on-highway diesel price has four parts: crude oil, refining costs and profits, distribution and marketing, and taxes. Crude averaged about 51% of the monthly retail price from 2004 through 2025. How each layer stacks up from the futures market to your tank is in how bulk diesel is priced; this week's numbers are in the U.S. diesel price report.

From the terminal to your tank

The refinery's job ends at the terminal rack. Ours starts there. FuelGo delivers clear on-road diesel, dyed off-road diesel, gasoline, DEF and R99 renewable diesel nationwide, 20 to 4,400 gallons per drop and transport loads up to 7,500 gallons through bulk fuel delivery. R99 isn't at every terminal; where it can't be pulled locally, we ship it by rail or barge.

Want price certainty? We offer fixed-price diesel contracts priced off NYMEX NY Harbor ULSD futures. Dispatch is staffed 24/7/365. Get a free quote or call 800-720-4546; a dispatcher replies within the hour.

Diesel from crude oil FAQ

Sources: U.S. EIA, Refining crude oil: the refining process (separation, conversion, treatment; furnaces and distillation units; cracking; blending) · U.S. EIA, Refining crude oil: inputs and outputs (2023 yields per barrel; 44.65 gallons; 6.3% processing gain) · U.S. EIA FAQ, gallons of gasoline and diesel from a barrel (11–13 gallons of ULSD) · U.S. EIA, Where our diesel comes from (2025 production, consumption, exports, imports; pipelines, terminals, trucks; batch testing) · U.S. EIA, Hydrocracking is an important source of diesel and jet fuel, Jan. 18, 2013 · U.S. EIA, Distillate yields at U.S. refineries are rising, Jan. 17, 2012 (yields vary with processes and crude) · Offshore Technology, Shell Canada ultra-low sulphur diesel project (hydrotreating, hydrogen sulfide, sulfur recovery) · U.S. EPA, Distillate Fuel No. 2 definition (90% point 540–640°F) · U.S. EPA, Diesel fuel standards rulemakings (15 ppm phase-in dates) · Fuel Oil News, Taking the mystery out of lubricity, Mar. 2010 (lubricity loss, 520-micron D975 limit in 2005, where additive is injected) · U.S. EIA, Biomass-based diesel fuels explained (renewable diesel vs. biodiesel) · U.S. EIA, Factors affecting diesel prices (crude about 51% of retail price, 2004–2025). Cetane minimum per ASTM D975, as cited in our #1 vs #2 diesel guide. The 30% share is a FuelGo calculation from EIA's 2023 figures.