When drivers see the price of gasoline rise or fall at the pump, crude oil prices are usually the first explanation they hear. And while crude oil is the largest single component of gasoline costs, there is another important part of the equation: oil refining.
Refineries transform crude oil into gasoline, diesel, jet fuel, and other petroleum products. The cost of performing that transformation—and the market value of the products coming out of the refinery—plays a major role in determining what consumers ultimately pay for gasoline.
From Crude Oil to Gasoline
Crude oil is not a single substance. It is a complex mixture of hydrocarbons that varies considerably depending on where it comes from. Some crude oils are relatively light and contain large amounts of hydrocarbons that can be converted into gasoline. Others are heavier and require more sophisticated processing.
A refinery separates crude oil into different components and then uses several processes to convert those components into commercially valuable fuels.
The basic process begins with distillation. Crude oil is heated and separated according to the boiling points of its various components. The refinery then uses additional processes—such as catalytic cracking, reforming, and treating—to produce fuels that meet required specifications.
These operations require substantial amounts of energy, equipment, labor, maintenance, and capital. Consequently, turning crude oil into gasoline has a cost of its own.
The Refining Margin
One of the most important concepts in understanding gasoline prices is the refining margin.
In simple terms, the refining margin is the difference between the value of the refined products a refinery produces and the cost of the crude oil used to make them.
For example, imagine a refinery purchases crude oil at a cost equivalent to $2.00 per gallon of crude and produces gasoline and other petroleum products worth $2.50 per gallon. The difference—before accounting for the refinery’s operating and other costs—is part of the refinery margin.
Margins are not fixed. They change according to supply and demand.
When gasoline demand is high while refinery capacity is limited, gasoline prices can rise relative to crude oil prices. Refining margins then increase. Conversely, if gasoline supplies are plentiful and demand is weak, margins can shrink.
This is one reason gasoline prices can sometimes move differently from crude oil prices.
Refinery Capacity Matters
The amount of available refining capacity is another major factor.
Refineries are enormous industrial facilities that require regular maintenance. Some units must periodically be shut down for inspections, repairs, and upgrades. Unexpected equipment failures can also temporarily reduce production.
If several refineries are operating below capacity at the same time, the supply of gasoline available to the market can decline. Even if crude oil prices remain unchanged, gasoline prices may rise because refiners have less ability to produce fuel.
This effect can be particularly noticeable during periods of strong seasonal demand.
Why Gasoline Specifications Affect Prices
Gasoline is not identical everywhere.
Different regions can require different fuel specifications to address air-quality concerns, seasonal temperatures, or other environmental requirements. In the United States, for example, some markets use specially formulated gasoline designed to reduce certain emissions.
Producing these specialized fuels can limit the number of refineries capable of supplying a particular market. Transportation between regions can also be difficult or expensive.
As a result, a disruption at one refinery can sometimes have a much larger effect on local gasoline prices than consumers might expect.
The Gasoline “Crack Spread”
Energy markets often use a measurement called the crack spread to estimate refinery economics.
The term comes from the process of “cracking” hydrocarbons, although the modern concept is broader than the physical cracking process itself. A crack spread compares the market prices of refined products with the price of crude oil.
A common example compares crude oil with gasoline and diesel prices.
When the spread becomes wider, refining gasoline and other products can become more profitable, assuming operating costs and other factors remain relatively stable. When the spread narrows, refinery economics become less attractive.
The crack spread therefore provides an important indication of how conditions in the refining industry may affect fuel prices.
Refiners Don’t Set Gasoline Prices Alone
It is important to understand that refiners do not simply choose the retail price motorists pay.
Gasoline passes through several stages between the oil field and the consumer. Crude oil must first be produced and transported. A refinery processes it into gasoline and other products. The gasoline is then transported to terminals and retail stations.
At the pump, the final price also includes taxes, transportation and distribution costs, and the retailer’s expenses and margin.
In broad terms, the price of gasoline can therefore be thought of as the combination of:
Crude oil cost + refining cost and margin + distribution and marketing costs + taxes = retail gasoline price
Each component can change independently.
Why Gasoline Prices Can Rise Even When Oil Prices Don’t
Consider a situation in which crude oil prices remain at $70 per barrel. If refinery outages suddenly reduce gasoline production, gasoline supplies can tighten.
Wholesale gasoline prices may rise because refiners and distributors have less fuel available. Retail gasoline prices can then increase even though the underlying crude oil price has not changed.
The opposite can happen as well. If refineries are operating efficiently and gasoline supplies are abundant, refining margins can fall. Gasoline prices may decline even without a major change in crude oil prices.
This helps explain why the relationship between oil prices and gasoline prices is not perfectly one-to-one.
Seasonal Changes
Refinery economics also change throughout the year.
Gasoline demand typically increases during the warmer months as driving activity rises. At the same time, refiners transition between seasonal gasoline formulations.
These changes can affect both production costs and market supply. If demand rises while available refining capacity is constrained, gasoline prices can increase rapidly.
Conversely, weaker demand in other periods can reduce pressure on refinery margins and wholesale gasoline prices.
The Bottom Line
Oil refining is the critical link between crude oil and the gasoline consumers put into their cars.
Crude oil provides the raw material, but refineries determine how that raw material is transformed into usable gasoline. The availability of refinery capacity, the cost of operating refineries, fuel specifications, seasonal demand, refinery outages, and the market value of gasoline all influence the refining margin.
That is why gasoline prices do not always move in perfect lockstep with crude oil prices.
The next time the price on a gas station sign changes, it is worth remembering that the number reflects an entire supply chain. The price of crude oil matters enormously—but the economics of turning crude into gasoline can determine how much of that cost ultimately reaches the driver.