The Surprisingly Complicated Process of Producing Gasoline

Gasoline is the best known and among the most important derivatives of oil, coveted worldwide for its use primarily as fuel for internal combustion engines. Today we will explore the process of producing gasoline, from the extraction of oil to its transformation into the fuel product that we all know just as gas.

To begin, let us first establish a clear concept of its definition. Gasoline is a product obtained from or through distillation, primarily used as fuel in most spark-ignition internal combustion engines as well as in stoves and lamps. The process to produce this product has been occurring for literally millions of years.

To obtain this fuel, the discovery of an oil field must first occur (duh). It is generally trapped in deep layers of reservoir rocks where the oil is more concentrated in the density of water. Above the oil field there exists natural gas (typically). Wells are drilled as deep as two miles or more. Once extracted, the crude oil is either taken to ships for export or sent to refineries, where the types of hydrocarbons it comprises are separated to be utilized later.

Distillation

Used almost exclusively as a fuel, refined oil becomes gasoline and becomes essential for the global transportation network, powering cars, trucks and other transportation systems. Once heated appropriately, the liquid compounds vaporize and also separate, and are subjected to a process known as fractional distillation. This process heats the crude oil allowing it to separate into different components based on their boiling points, with the lighter components (diesel, gasoline, and naptha), all rise to the top.  Heavier components like heating oil and residual fuel oil settle to the bottom. All this occurs by means of what is referred to as an atmospheric distillation tower. This is the first step in the refining process, known as distillation.

Conversion
Next, a process known as conversion must occur. In this step “cracking” or other methods are used to break down larger hydrocarbon molecules into smaller ones. Cracking involves using a combination of heat, pressure and catalysts which allows conversion of heavy oil into lighter, more valuable components such as gas. The cracking process is highly technical in nature and cracker plants are few and incredibly expensive to construct. The last new cracker plant I know of was just finished near Monaco, Pennsylvania in 2022. Cracking can also be made to occur using hydrocracking or catalytic cracking in lieu of the typically process as described here.

Treatment
During the treatment stage, various products are blended to create specific fuel products. It also entails removing the sulfur and other impurities which would cause the fuel to burn less lean or would generate unnecessary pollution. Almost all of the premier petroleum products require, in order to maximize efficiency and minimize production costs, oil with a low sulfur content, and a relatively thin oil with a high API. Further enhancement of the produced product is sometimes performed by the addition of various octane enhancers.

Distribution
The finished products are separated and brought to market in their own state or in a blended state to create specific fuel, like gasoline. Items such as ethane, butane, propane, or pentane occur naturally in the production stream and do not require blending or enhancements, unless they themselves are being used for said purpose.

Pipelines are the preferred means of transportation, assuming the oil will flow freely through it. Some oil sources, including that derived from Canadian oil sands, require blending with a high API oil such as that found in Ohio’s Utica Shale. Others, like the waxy oil derived from the Uinita Basin in Utah, require heating in order to flow unimpeded through pipelines.
Sometimes transportation must be carried out my means of tankers, especially between refinery and final destination. Of course, fuel tankers (ships) are also used to ship mega-cargos of the product internationally. Rail cars are still used for transport also, despite the disastrous wreck near East Palestine, OH during 2023. This one incident caused major US railroads to promise an “overhaul of all safety procedures in the industry”. The accident has cost Norfolk-Southern a minimum of $50M to date, including settlements with the city of East Palestine and numerous individuals. As recently as January of this year, suits continued to be filed, including that alleging the death of seven individuals as a direct result of the derailment.

Two Types of Gasoline?
Most travelers still budget a considerable part of their summer vacation towards gas, fully expecting the typical rise in prices by Memorial Day. Who’s behind this summer conspiracy and why does it occur seemingly each and every year? The answers may surprise you in that there are legitimate costs associated with producing an approved fuel that the EPA will allow you to sell in July versus, say…December.

Because summer heat creates or contributes to the creation of an inversion layer -- an immobile layer of air that often traps pollutants in the lower atmosphere, the government requires adjustment of the product fuel mix approved for consumer vehicles during summer use. Atmospheric conditions seem to require the EPA to consider smog and ozone to be of greatest concern during summer months.

Sumer-grade fuel is marginally more eco-friendly because it evaporates more quickly than those approved for winter-grade sales. This is due to its different Reid Vapor Pressure (RVP). RVP is the vapor pressure of gasoline measured at 100 degrees Fahrenheit. A fuel’s RVP is influenced greatly by the ingredients which are approved to make each particular blend. The EPA is concerned about such because they believe this evaporation contributes to ozone formation.

Winter-grade fuel uses more butane, with its high RVP of 52 PSI, as an additive and consequently actually costs less to produce. Butane is inexpensive and plentiful and is attractive in that it has an octane rating above 90%, almost equal to that of premium gasoline. However, its volatility limits the amount of butane that can be used in summer-grade gasoline (usually not to exceed 2%). Consequently, less butane equals higher costs leading to higher prices. It really is a pretty legitimate answer to a problem many ponder each year.

Winter or Summer-grade, gasoline must have an RVP not to exceed 14.7 PSI (pounds per square inch), which is normal atmospheric pressure. Otherwise, internal pressure could build up in the tank and the fuel could boil and evaporate. EPA's standards mandate, depending on which part of the country you are from, an RVP below 9.0 PSI or 7.8 PSI for summer-grade fuel. Because of these varying RVP standards, 20 or more types of boutique fuel blends will be sold throughout the U.S. before summer’s end. Naturally, California has its own particular requirements.

A typical summer-grade gas is composed of fluid catalytic cracker gasoline, 40%; straight-run gasoline (directly from crude oil distillation), 15%; reformate, 18%; and butane, 2%. Winter-grade gasoline obviously contains more butane, which allows prices to fall accordingly.

The EPA defines April to June as the "transition season" for fuel production. Refineries begin summer-blend production by March of each year. By June 1, most have switched to selling summer-grade gas. Upstream facilities necessary to fuel pumping stations and the like have until May 1 to comply. By September, the trend is reversed, and the RVP allowance is again changed.

And the cycle continues…