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.
It was specified in 1990 by the U.S. government as a replacement for government diesel fueled vehicles.
The U.S. Air Force replaced JP-4 with JP-8 completely by the fall of 1996, to use a less flammable, less hazardous fuel for better safety and combat survivability.
Outside of powering aircraft, JP-8 is used as a fuel for heaters, stoves, tanks, by the U.S. military as a replacement for diesel fuel in the engines of nearly all tactical ground vehicles and electrical generators, and as a coolant in engines and some other aircraft components. The use of a single fuel greatly simplifies logistics.
JP-8 is formulated with icing inhibitor, corrosion inhibitors, lubricants, and antistatic agents, and less benzene (a carcinogen) and less 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.
When used in highly supercharged diesel engines with the corresponding low compression ratio of about only 14:1 or below, JP-8 causes troubles during cold start and idling due to low compression temperatures and following ignition delay because 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 the increased wear in outlet valve seats in the cylinder heads, because a minimum content of sulfur is not specified in MIL-DTL-83133G. Sulfur in fuels contributes normally to build up damping soot layers in these valve seats. According to the notes in this standard it is intended to install a value for the cetane index in one of the next releases.
Workers have complained of smelling and tasting JP-8 for hours after exposure. As JP-8 is less volatile, it remains on the contaminated surfaces for longer time, increasing the risk of exposure.
JP-8+100 (F-37) is a version of JP-8 with an additive that increases its thermal stability by 56°C (a difference of 100°F). The additive is a combination of a surfactant, metal deactivator, and an antioxidant, and was introduced in 1994 to reduce choking and fouling in engine fuel systems. Commercially, this additive is used in Boeing aircraft operated by KLM, and in police helicopters in Tampa, Florida. JP-8+100 is also used for Canadian Forces CP-140 Aurora, CC-130 Hercules and the CC-115 Buffalo.
See also 
- MIL-DTL-83133 technical specifications (includes JP-8) United States Defense Energy Support Center
- MIL-DTL-46162 referee fuel Diesel and JP-8 United States Defense Energy Support Center
- Current United States Department of Defense Fuel Prices