Testing For Differences

In well-lit hangar and separated into nice clean glass containers, its easy to tell the difference between 100LL aviation gasoline and kerosene-based turbine fuels like Jet A. In the field, not so much: Fuel tanks are dark places, and shining a flashlight onto a liquid rarely helps identify what it is. Draining some fuel into a sampling cup and comparing it to what youre looking for may not help, either, since jet fuel typically is clear (or straw-colored) and may not appreciably change the tint of 100LL.

Editorial Staff

Wednesday, April 22, 2015 at 12:00 AM ET

Verified

Key Takeaways:

Distinguishing 100LL avgas from jet fuel in the field is challenging due to similar appearance and the unreliability of color or smell alone.
One simple ramp test involves placing a drop on your finger: avgas will evaporate quickly, feeling cool, while jet fuel will feel oily and evaporate slowly.
Another effective field test is to put a few drops on a white paper towel: avgas will evaporate rapidly, leaving a slight blue stain, whereas jet fuel will leave a persistent oily ring.

See a mistake? Contact us.

In well-lit hangar and separated into nice clean glass containers, it’s easy to tell the difference between 100LL aviation gasoline and kerosene-based turbine fuels like Jet A. In the field, not so much: Fuel tanks are dark places, and shining a flashlight onto a liquid rarely helps identify what it is. Draining some fuel into a sampling cup and comparing it to what you’re looking for may not help, either, since jet fuel typically is clear (or straw-colored) and may not appreciably change the tint of 100LL.

Jet A does smell differently than aviation gasoline (and nothing smells better than avgas!)—its odor is more like kerosene or diesel fuel. But odor alone won’t help determine if there’s Jet A in your avgas. Instead, you’ll have to investigate even further. There are two basic ramp tests a pilot can use to determine if there’s any jet fuel in the avgas.