What is the Difference Between Jet Fuel & Diesel Fuel?

Jet fuel of types A and A-1 is composed of mostly kerosene, and Jet B is a naptha-kerosene mix. Diesel gas is approx. 75 percent kerosene, with added lubricants and a low-sulfur content.

Diesel gas is heavier than jet fuel, with a higher number of slightly larger hydrocarbon chains, though both are primarily paraffin oils (kerosene). Diesel is more viscous than jet fuels.

Jet fuel often has antifreeze and anti-microbial agents, static dissipaters and corrosion inhibitors added to improve performance in aeronautical engines, whose ambient temperature often varies wildly during flight.

Diesel has lubricant additives to promote healthy engine function–using kerosene or Jet-A fuels in a diesel engine may cause damage due to its lower levels of lubricants. Diesel also contains a dye added to prove it has been taxed.

According to Inspectapedia.com, diesel has a higher BTU output and more energy per unit than does Jet-A fuel.

While many attest to using 50-50 ratios of jet/diesel in diesel engines, this will cause the engine to run hotter and have a lower mpg rating. It will also void many warranties by the manufacturer. Jet-A is more similar to Diesel #1, which is lighter than Diesel #2 (automotive diesel), and so is not a perfect substitute, but in emergency situations is a potential fuel source. Jet-A usage will not cause instant physical damage but long-term wear will increase due to lack of lubrication, different burn temperatures and energy output.