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Why is jet fuel red?

Jet fuel comes in a variety of colors depending on its composition and additives. While most commercial jet fuels are clear or straw-colored, some specialty fuels contain dyes that turn them bright red. This eye-catching color serves an important purpose – to quickly identify and differentiate types of jet fuel.

The History of Red Jet Fuel

Adding red dye to jet fuel originated in the 1950s when the United States Air Force began using JP-4 jet fuel. JP-4 was formulated to have a lower freezing point than earlier jet fuels, making it suitable for high-altitude flight. However, the Air Force was also concerned about misfueling its aircraft with gasoline, which was dyed red at the time.

To prevent potential mix-ups, the Air Force started adding their own red dye to JP-4 jet fuel. This allowed ground crews to easily spot jet fuel and avoid accidental contamination. The red colorant they chose was called Akulon Red F cone dye. It produced a vibrant cherry-red color that was highly visible.

When the Air Force switched to less freeze-sensitive JP-8 fuel in the 1990s, they continued dyeing it red for identification purposes. The colored JP-8 became known as “F-34” or “red jet fuel” in military parlance.

Decade Jet Fuel Type Color
1950s JP-4 Red
1990s-present JP-8 Red

This practice of dyeing certain jet fuels red continues today in military and some civilian operations. The distinct color helps users quickly identify the specific fuel type.

Why Red Dye is Added

There are several key reasons why red dye is added to jet fuels like JP-8:

  • To differentiate fuel types – Red color indicates a specialty jet fuel specification.
  • To prevent misfueling – Vivid red color is easy to distinguish from other clear fuels.
  • To detect leaks and contamination – Red stains help identify spills, leaks, and contamination.
  • For inventory control – Color coding helps track jet fuel stocks and use.
  • As a security measure – Dye aids in identifying and securing sensitive military jet fuels.

The most important reason is to positively identify the particular jet fuel type. Red dye provides an unmistakable visual marker that ground crews can rely on. Just a quick glance at the fuel color confirms they are using the correct specialized fuel.

The dye also helps prevent potential mix-ups with other types of fuels. Clear jet fuel could be confused with kerosene or gasoline, especially in low light conditions. But vivid red fuel stands out as jet fuel. Misfueling mistakes can lead to serious consequences, so the red color acts as fail-safe.

Additionally, leaks or spills of red jet fuel are easy to see and clean up. The dye highlights contamination problems. Inventory and security are also aided by the unique color identifier.

Modern Red-Dyed Jet Fuels

While civilian aircraft mostly use clear or straw-colored fuels, red jet fuel lives on in some military and alternative jet fuel applications:

Jet Fuel Type Description
JP-8 Standard red dyed jet fuel for the US Air Force
JP-5 Navy equivalent of JP-8 also dyed red
JP-8+100 Improved JP-8 with additive, colored red
JP-8+220 Alternative fuel blend with SynJet, dyed red

The most common red jet fuel is JP-8, which the US Air Force has exclusively used since the 1990s. They dye it red for the visibility and anti-contamination benefits. The US Navy uses a similar red-dyed fuel called JP-5.

JP-8+100 is an improved variant of JP-8 with an additive called DiEGME that provides more thermal stability. It also retains the familiar red color for identification. JP-8+220 is a more radical departure – it blends traditional JP-8 with a synthetic paraffinic kerosene called SynJet. This biofuel mixture yields superior performance and still carries the red marker dye.

How Red Dye is Added

There are two approved processes for adding red dye to jet fuel:

  1. Dye Injection – A concentrated liquid dye solution is injected into the fuel stream as it travels between storage tanks and transports. It is blended in-line.
  2. Pre-Doping – The dye is added directly to fuel storage tanks and allowed to disperse. Fuel is pre-dyed before distribution.

The injection method allows flexibility in when and where to add the dye. It can be applied at the refinery, terminal storage facility, airport fuel depot, or truck loading rack. Injection dosing rates typically range from 1-4 ppm (parts per million) of dye solution.

Pre-doping directly colors the full volume of fuel in a storage tank. This ensures uniform dye dispersion before further handling. Dosing rates are lower, such as 0.5 ppm. The limitation is that all fuel coming from that tank will be red-dyed.

Both methods work equally well when proper dosing and mixing procedures are followed. The dye distributes evenly and remains stable. Regular color checks confirm consistent dye levels are maintained.

Color Characteristics

Jet fuel is dyed using F-4177 Red Dye. This is an alcohol-soluble aniline-based aromatic azo dye. It has excellent stability in hydrocarbon fuels. The red color exhibits these properties:

  • Hue – Bright red with a slight orange tint.
  • Intensity – High chromaticity for maximum visibility.
  • Opacity – Clear, transparent red color.
  • Shade – Medium-dark red, approximating a cherry color.
  • Density – Heavier dye molecules settle slowly over time.
  • Stability – Dye remains stable for 6 months under normal conditions.

The dye gives jet fuel an opaque, cherry-red color when freshly applied. Over time, the heavier dye molecules will slowly settle. This can cause the top portion of a fuel tank or transport to appear more orange, with deeper red on the bottom. Recirculation or mixing restores an even color distribution.

The dye has negligible effect on the physical properties or performance of the base jet fuel. It causes no issues with pumping, atomization, or combustion. There are no filtration or maintenance problems from adding this soluble colorant liquid.

Storage and Handling

Red-dyed jet fuels should be stored and handled like standard fuels with a few additional precautions:

  • Segregate tanks/plumbing to avoid cross-contamination.
  • Add dye upstream to allow full dispersion and dilution.
  • Perform periodic color checks and test dye concentration.
  • Investigate any color discrepancies or anomalies.
  • Avoid prolonged direct sunlight exposure which fades color.

Care should be taken to keep red jet fuel from mixing with other clear fuels. Separate storage and piping prevents dilution of the color. Always add dye as early in the handling process as possible.

Testing dye levels ensures proper concentration. Any significant color variation may indicate contamination or handling issues. Avoid storing red jet fuel in direct sun which can bleach the dye over time.

With proper precautions, red-dyed fuels can be stored and used interchangeably with clear jet fuel. The dye remains homogenously dispersed with no adverse effects.


Red-colored jet fuel serves an important purpose by providing easy visual identification of specific fuel types. Military operations initially drove the use of red dyes starting in the 1950s. This practice continues today with red-dyed versions of JP-8, JP-5, and other jet fuels.

The red color offers many benefits such as preventing misfueling mistakes, spotting leaks/spills, improving inventory control, and enhancing security. It also aids in distinguishing specialty fuels like JP-8+100 and JP-8+220 blends. The dyeing process is simple and causes no changes to fuel performance.

So while most civilian jets use clear jet fuel, there are still some applications that benefit from red-dyed fuel. The vibrant color makes it easy to definitively identify those special jet fuel types at a glance. Red jet fuel will continue serving critical aviation coloring needs well into the future.