JP-8

JP-8, or JP8 (for "Jet Propellant 8"), is a jet fuel, specified and used widely by the US military. It is specified by MIL-DTL-83133 and British Defence Standard 91-87, and similar to commercial aviation's Jet A-1, but with the addition of corrosion inhibitor and anti-icing additives.

A kerosene-based fuel, JP-8 is projected to remain in use at least until 2025. It was first introduced at NATO bases in 1978. Its NATO code is F-34.

Usage
The United States Air Force replaced JP-4 with JP-8 completely by the end of 1995, to use a less flammable, less hazardous fuel for better safety and combat survivability.

JP-8 is formulated with an icing inhibitor, corrosion inhibitor–lubricants, and antistatic agents, and contains less benzene (a carcinogen) and n-hexane (a neurotoxin) than JP-4. However, it also smells stronger than JP-4. JP-8 has an oily feel to the touch, while JP-4 feels more like a solvent.

The United States Navy uses a similar formula, JP-5. JP-5 has an even higher flash point of > 140 °F (60 °C), but also a higher cost. The U.S. Navy Seabees use JP-8 in construction and tactical equipment.

Single-fuel concept
JP-8 was specified in 1990 by the U.S. government as a replacement for government diesel fueled vehicles. This is in the wider context of the 1986 NATO Single-Fuel Concept agreement, in which F-34 (JP-8) is to replace F-54 (diesel fuel) in land vehicles and F-40 (JP-4) in land-based turbine aircraft to simplify logistics. It is also used as coolant in engines and some other aircraft components.

Beyond use in vehicles from trucks to tanks to planes, JP-8 is used in U.S. Army heaters and stoves.

Diesel problems
When used in highly turbocharged diesel engines with the corresponding low compression ratio (e.g. 14:1 or lower), JP-8 causes troubles during cold start and idling due to low compression temperatures and subsequent ignition delay because the cetane index is not specified in MIL-DTL-83133G to 40 or higher. Because lubricity to the BOCLE method is not specified in MIL-DTL-83133G, modern common-rail diesel engines can experience wear problems in high-pressure fuel pumps and injectors. Another problem in diesel engines can be increased wear to exhaust valve seats in the cylinder heads, because a maximum sulfur content is not specified in MIL-DTL-83133G. Sulfur in fuel normally contributes to a build-up of soot layers on these valve seats. According to the notes in this standard, it is intended to include a cetane index value in one of the next releases. MIL-DTL-83133J sets the maximum sulfur content at 0.30%. It however only requires a cetane number of 40 after addition of FT-SPK (synthetic jet fuel).

The use of jet fuel in diesel engines has caused some minor issues, none of which were discovered in the Fort Bliss test with JP-8. During Desert Shield and Desert Storm, commercial Jet A1 was used as the single-fuel and failed engines with Stanadyne fuel-injection pumps missing an elastomer insert retrofit. Other than that, JP-8 slightly reduces torque and fuel economy due to its lower density and viscosity compared to diesel fuel. Engine modification can offset this issue.

Health concerns
Workers have complained of smelling and tasting JP-8 for hours after exposure. As JP-8 is less volatile than standard diesel fuel, it remains on the contaminated surfaces for longer time, increasing the risk of exposure. JP-8 exposure has also been linked to hearing problems, but rather than being unable to hear sounds, the brain has a hard time deciphering the message. Dr. O'neil Guthrie, a research scientist and clinical audiologist with the United States Department of Veterans Affairs Loma Linda Healthcare System in California, has compared the central auditory processing disorder to dyslexia for the ears.

In 2001, Texas Tech University's Institute of Environmental and Human Health and the United States Air Force conducted an 18-month study of the health effects of JP-8 on 339 active duty personnel at six US Air Force installations. The study found that Air Force workers who were exposed to JP-8 were no more likely to seek medical attention than workers who were not exposed to JP-8 on the job. Personnel in the high- and moderate-exposure categories self-reported greater amounts of symptoms such as headaches, dizziness, difficulty breathing, general weakness, trouble concentrating, forgetfulness, and trouble gripping things.

Variants
JP-8+100 (F-37) is a variant of JP-8 augmented with the additive Spec-Aid 8Q462, also known as Aeroshell Performance Additive 101, created by BetzDearborn (now GE Betz). The additive increases the thermal stability of JP-8 by 100 °F (increase of 56 °C), hence the designation "+100". Spec-Aid 8Q462 was introduced in 1994 to reduce choking and fouling in engine fuel systems and is a combination of a surfactant, metal deactivator, and an antioxidant. It is added to JP-8 at a ratio of 256 ppm to create JP-8+100, at an added cost of $5 per 1000 gallons of fuel. Commercially, this additive is used in police helicopters in Tampa, Florida. JP-8+100 is also used for Canadian Forces CP-140 Aurora, CC-130 Hercules, CF-18 Hornet and the CC-115 Buffalo.

F-35 is a variant without icing inhibitor. The only requried additive is a static dissipater.

JP-8+100LT is a variant of JP-8+100, with additives to facilitate low-temperature performance. It is considered as a logistically friendly low-cost replacement of the JPTS fuel for the Lockheed U-2 airplane.

F-24 is commercial Jet A fuel (ASTM D1655) with the additive package required for JP-8 (SDA, CI/LI, FSII) added by the military. The intention is to lower costs by using commercially-available fuel. The resulting fuel has identical properties to JP-8, save for a higher freezing-point specification. The U.S. military has switched to F-24 in domestic (excluding Alaska) sites in 2012. In 2018, it was found that the F-24 mixture could deteriorate during transport causing much reduced thermal stability, but addition of the +100 (8Q462) additive was enough to salvage degraded fuel.

F-27 is F-24 with the +100 additive package.

JP-8+225 is a planned variant of JP-8 that increases thermal stability by 225 F-change. Such a fuel would match the thermal stability of JP-7 and become a lower-cost replacement should it exist.