Distillate fuel is a broad classification for liquid hydrocarbon products refined from crude oil. This fuel category is recognized for its lightness, low viscosity, and cleaner-burning properties compared to heavier residual fuel oils. Distillates are integral to the global economy, serving as a primary energy source for transportation, heating, and power generation. The defining characteristic is the separation method from raw petroleum.
How Distillate Fuel is Manufactured
The production process that gives distillate fuel its name is fractional distillation, occurring within a tall refining column. Crude oil is heated to high temperatures, often exceeding 600° Fahrenheit, turning hydrocarbons into a superheated vapor. This vapor is then piped into the base of the distillation column, where it begins to rise.
As the vapor ascends the column, it naturally cools, causing different hydrocarbon molecules to condense back into liquid form at varying temperatures, corresponding to their boiling points. Heavier, longer-chain molecules condense lower down. Lighter, shorter-chain molecules travel higher. Distillate fuels are collected as “middle distillates,” condensing in the tower’s middle sections.
This placement is between lighter products, such as gasoline and naphtha, drawn off near the top, and heavy residual products, like asphalt and residual fuel oil, which remain at the bottom. The resulting liquid is a blend of hydrocarbons with a specific range of molecular weights and boiling points. This blend is processed into final fuel products. Refining removes impurities, such as sulfur, to meet modern environmental and engine specifications.
Major Types of Distillate Fuels
The distillate family includes several major products, each tailored for a specific application based on chemical composition and performance characteristics. Diesel fuel is the most widely recognized distillate, graded into two types based on refinement. No. 2 Diesel is the most common form, featuring higher energy content, better lubricating properties, and a lower cost due to less intensive refinement.
No. 1 Diesel is a lighter, more refined product with a lower viscosity, making it resistant to gelling and clouding in cold temperatures. This improved cold-weather performance comes at the expense of lower energy content and a higher price point. In regions with seasonal temperature swings, No. 1 and No. 2 diesel are blended during winter months to provide a balance of cold-flow properties and energy density.
Another prominent distillate is heating oil, which is chemically similar to No. 2 Diesel, though it contains a different additive package since it is not designed for high-compression engines. No. 2 Fuel Oil is the standard grade used in residential and commercial furnaces for space heating. Kerosene is a lighter distillate, referred to as No. 1 Fuel Oil, used for specific heating needs and is the base for most jet fuels.
Common Industrial and Consumer Uses
Distillate fuels are the lifeblood of the heavy-duty transportation sector, where high energy density and efficiency are utilized in compression-ignition engines. No. 2 Diesel powers the majority of commercial trucking fleets, railroad locomotives, and heavy construction equipment. The marine industry relies on distillate marine gas oil for propulsion, particularly where cleaner-burning fuels are mandated.
Beyond transportation, distillate fuels are widely used for energy generation in industrial and commercial settings. They are the preferred fuel source for backup power systems and emergency generators due to easy storage and reliable ignition. Stationary engines ensure continuity for hospitals, data centers, and telecommunications infrastructure during electrical grid outages.
In the consumer market, heating oil is the main application, especially in the northeastern United States and colder climates, providing warmth to millions of homes. Kerosene serves a niche in heating, used in portable heaters or where a clean-burning fuel is necessary. These diverse applications solidify distillate fuels’ position as a globally significant energy commodity.