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SESK: Stuff Everyone Should Know · sesk.info/pilot-100ll-blue

During preflight, what color should a sample of 100LL avgas be?

Blue.

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  1. Red
  2. Green
  3. Blue ✔

Why: Avgas grades are dyed for easy identification. 100LL, the most common grade in the US, is dyed blue. Holding the sample against a white background helps you see the faint color.

Huh, didn't know that: 80/87 avgas is dyed red and 100/130 is dyed green.

The dad joke
Why was the 100LL sad? It was feeling a little blue.
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References

Answer: Blue. Avgas grades are dyed for easy identification. 100LL, the most common grade in the US, is dyed blue. Holding the sample against a white background helps you see the faint color.

  1. Airplane Flying Handbook FAA-H-8083-3C Chapter 2, Ground Operations www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/airplane_handbook/03_afh_ch2.pdf
    80/87 is dyed red; 100LL is dyed blue; and 100/130 is dyed green.
    Checked 2026-10-09.

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