What is Jet Fuel: The Differences Between Kerosene and Jet Fuel

Refined from crude oil through a process known as fractional distillation, jet fuel is fundamentally a more refined version of kerosene. There are also different types of jet fuel that have many differences – from boiling point to octane rating to lower freezing point to aromatics, these types of aviation fuel are nuanced in many ways. Used for centuries, kerosene has played a pivotal role in heating, lighting, and cooking across the globe. Today, it's used at a rate of about 1.2 million barrels per day.

Kerosene vs. Gasoline

'Kerosene is historically known as paraffin. After petroleum refining, paraffin remains as a waxy residue, which gives us a clue about the relationship between kerosene and jet fuel. This relationship is essential to understanding their use in aviation fuel, particularly for turbine engines within the aviation industry, including civil aviation and air force applications.

Crude oil, rich in aliphatic hydrocarbons (compounds mainly comprising hydrogen, carbon, and possible sulfur impurities), undergoes fractional distillation. This refining process involves heating these hydrocarbons at various temperatures, segregating them into different chain lengths from the light naphthas to heavier chains that form substances like paraffin.

Kerosene is less volatile than gasoline due to its heavier hydrocarbon chains. This difference results in a higher flash point for kerosene, improving safety during storage and transport, a crucial factor in aviation fuel for both commercial airliners and military aircraft.

Despite being less abundant than aviation gasoline, kerosene forms a significant part of refinery products. The U.S. Energy Information Administration (EIA) states that a 42-gallon barrel of crude oil yields around 20 gallons of gasoline and 16 gallons of other distillates, including jet fuel and diesel fuel.

Kerosene, jet fuel, and diesel are interconnected, sharing similar classes of hydrocarbons. The refinement level is what differentiates them - jet fuel undergoes a more intensive refining process than kerosene, which is more refined than diesel. Indian Oil, a regulator of petroleum products in India, designates jet fuel as SKF, or "superior kerosene fuel."

Jet fuel adheres to stricter standards than kerosene, particularly concerning its freezing point, flash point, viscosity, sulfur content, and calorific value. It also contains additives that enhance cleaner burning and efficiency, as well as preventing ice formation and corrosion. This helps preserve the aviation turbine fuel system.

Different grades of jet fuel exist, each serving specific purposes. Jet A is almost identical to kerosene and was widely used in Europe post-World War II. Jet B and JP-4 are mixtures of kerosene and gasoline. They are mainly used for military aircraft due to their low freezing point and higher volatility. JP-5, or high-flash-point kerosene, is safer to handle, and JP-8 is a kerosene blend used as a diesel fuel substitute.

Grades of Jet Fuel

• ‌Jet A,‌ which is the fuel that was widely used in Europe after World War II, is almost identical to kerosene. Its widespread use on the continent was due to the fact that it was more available than gasoline. Another grade in common use is ‌Jet A-1‌. Together, these are the fuels used more commonly by commercial airliners.

• ‌Jet B and JP-4‌ ("JP" stands for jet propulsion) are mixtures of kerosene (30 percent) and gasoline (70 percent). They include a larger concentration of the light hydrocarbons and naphthas than Jet A, so they weigh less, which is a desirable characteristic for aviation. However, they have lower flash points and are more dangerous to handle. Because they have low freezing points, they are used for military purposes in the far north.

• ‌JP-5‌ is also known as high-flash-point kerosene. It is safer to handle than even Jet A and is required for aircraft aboard aircraft carriers as well as for presidential fleet aircraft. Its composition includes approximately 53 percent C₉ to C₁₆ liquid paraffins (hydrocarbons) with the rest made up of cycloparaffins, aromatics and olefins.

• ‌JP-8‌ is a 100 percent kerosene blend and is an acceptable substitute for diesel fuel. It is the fuel most widely used for military aircraft, and its use is expected to continue until 2025. Unlike JP-4, which feels like a solvent to the touch, JP-8 feels somewhat thick and oily.

Jet engines use kerosene-based fuels like Jet A, while propeller-powered aircraft with piston engines require a gasoline-type fuel, typically avgas, a higher-octane variant of motor fuel (mogas).

Jet A could theoretically be used to power kerosene heaters or diesel vehicles, given it burns more efficiently than diesel fuel. However, the absence of lubricating and cleansing additives in jet fuels, necessary for diesel engines, could lead to issues, requiring frequent maintenance.

Kerosene heaters designed for 1-K and 2-K kerosene should not use jet fuel as it burns at significantly higher temperatures, posing a fire or explosion risk. With a global shift toward biofuels and sustainable aviation fuel, ASTM (American Society for Testing and Materials) guidelines, fuel oil standards, and FAA (Federal Aviation Administration) regulations continue to evolve to ensure safety and efficiency. It's essential to consider the impact of such fuels on factors such as emissions, high altitudes performance, natural gas compatibility, lubrication, and low-temperature performance.

Supplemental List of Differences between Kerosene and Jet Fuel

The main differences between kerosene and jet fuel are:

• ‌Composition‌ - Jet fuels like Jet A and JP-8 are kerosene-based, but have other compounds added to meet performance specifications. Kerosene alone does not meet jet fuel standards.
• ‌Additives‌ - Jet fuels contain antioxidants, anti-static agents, corrosion inhibitors, and other additives not found in plain kerosene. These help stabilize and protect jet fuel systems.
• ‌Freezing Point‌ - Jet fuels are refined to have far lower freezing points than kerosene to prevent gelling at high altitudes. Jet A has a -40°C freezing point.
• ‌Flash Point‌ - While both have high flash points, jet fuels typically have higher minimum flash point standards (38°C for Jet A) than kerosene for enhanced fire safety.
• ‌Energy Density‌ - Jet fuel formulations have a slightly higher energy density than regular kerosene, producing more power per gallon burned.
• ‌Cleanliness Standards‌ - Jet fuel must meet extremely strict cleanliness specifications to avoid contaminating and damaging jet engine systems during use.
• ‌Usage‌ - Jet fuel is solely used for turbine engines in aviation. Kerosene is used in various other applications like heating, lighting, and rockets.