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 aviation gasoline from kerosene-based jet fuel like Jet A is challenging in the field due to visual similarities in dark fuel tanks, despite their distinct odors.
Pilots can perform two basic ramp tests to determine if jet fuel has contaminated avgas.
The first test involves evaporation: avgas quickly evaporates from a finger, causing cooling, while jet fuel feels oily and evaporates much slower. The second test uses a plain white paper towel: avgas evaporates quickly, leaving a slight blue stain, whereas jet fuel leaves a persistent oily ring.

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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.