Cessna issues strong warning against use of ethanol in fuels

In a Service Letter issued May 18, Cessna issued a strong warning against the use of ethanol in fuels powering its aircraft. Titled “Ethanol-based fuel not approved for use in Cessna airplanes,” this Service Letter documents Cessna’s exhaustive testing of AGE-85, an 85% ethanol blend that has been championed in recent years by South Dakota State University and others.

Cessna lists a number of serious consequences when using fuels containing ethanol:

  • To match detonation characteristics at high power settings, the utilization of ethanol-based fuels requires fuel flow volume increases of nearly 40% as compared to 100LL fuel. This means that the current published airplane performance information is not accurate when using ethanol-based fuels.
  • Ethanol-based fuels are not compatible with some fuel system components, causing extreme corrosion of ferrous components, the formation of salt deposits, jelly-like deposits on fuel strainer screens, and internal separation of portions of rubber fuel tanks.
  • The use of ethanol-based fuels can negatively affect electric fuel pumps by increasing internal wear and causing undesirable spark generation.
  • AGE-85 is not compatible with some fuel quantity gauging systems and may cause erroneous fuel
    quantity indications.
  • AGE-85 is capable of dissolving large amounts of water at conditions down to minus 77ºF,
    impeding the detection and removal of water from the fuel system.
  • AGE-85 may block fuel filter, affecting fuel flow.
  • AGE-85 experiences heavy evaporation losses.

Cessna’s document also issues this warning: These tests and evaluations also suggest that operational safety may be compromised by the use of ethanol-based fuels.

From discussions your bloggers have had with an official involved in these tests, Cessna’s recommends against the use of any levels of ethanol in fuels used in its aircraft, not only AGE-85.  Its conclusions are in stark contrast to claims made by AGE-85 proponents, for instance at the American Coalition for Ethanol or at e85Tips.

The GAfuels Blog is written by three private pilots concerned about the future availability of fuels for piston-engine aircraft. They are:

  • Dean Billing (Sisters, Ore.) – an expert on autogas and ethanol
  • Kent Misegades (Cary, N.C.) – an aerospace engineer and aviation journalist
  • Todd Petersen (Minden, Neb.) – former aerial applicator and owner of more than 150 Mogas STCs for aircraft

For a list of airports that have ethanol-free fuel and those no longer pumping it, compiled by the authors, follow this link.


  1. says


    “AGE-85 is capable of dissolving large amounts of water at conditions down to minus 77ºF
    impeding the detection and removal of water from the fuel system.”

    What impedes the detection and removal of water from the fuel tanks of Cessna aircraft is the fuel tanks do not meet the certification requirements of CAR 3.444 or FAR 23.971.
    Both CAR and FAR, for the most part, states “any hazardous quantity of water from any where in the fuel tank must come to the sump drain as the aircraft sits in its normal ground attitude to be eliminated”. You should not blindly believe in the FAA certification of Cessna aircraft. Undetectable water does hide in the fuel tanks and the preflight procedure is an effort in futility. A simple test on any Cessna parked anywhere will immediately demonstrate that the sumping of Cessna fuel tanks does not work as certified. Take a 16 ounce Dixie cup full of red dyed water, pour it into the fuel tank as the aircraft sits in its normal ground attitude, then go to the sump drain and see if you can positively detect and eliminate the same 16 ounces you just poured into the fuel tanks. GOOD LUCK.

    Oh, and by the way, have you seen the new SAIB CE10-40R1 just released warning pilots to try and keep water out of the fuel tanks of the 100, 200 and 300 Cessna series aircraft. Why would you suspect this effort in futility would come out if there is not a problem with the certification of Cessna fuel tanks and the preflight procedure? One of the suggestions in the SAIB is to become more familiar with your fuel provider, ask to see their test sheet where they have checked for water in the fuel at the FBO, fuel truck checks, etc. You are to do this where ever you fly. Can you just imagine how the FBO would look at you and most likely refuse you service? The problem of UNDETECTABLE WATER IN CESSNA FUEL TANKS IS THE FUEL TANKS IN THE AIRCRAFT WINGS DO NOT MEET CERTIFICATION. It does not matter where the aircraft is parked, it does not matter if it sits out in the rain, it does not matter how often the aircraft is flown. What matters is if your aircraft is sabotaged, gets mis-fueled, condensates, or for what ever reason has water in the fuel, you during the preflight positively detect that water and eliminate it before take off. The problem is not the fuel caps, not the cap seals, not that it has rained for forty days and forty nights as the aircraft sits outside. The PROBLEM IS THE CESSNA AIRCRAFT DOES NOT MEET CERTIFICATION. The problem is not the pilot who sees no water in his sump cup, then takes off, the engine sputters, runs rough and quits and the aircraft hits the ground. The pilot and his passengers die and the inept NTSB writes the engine failure off 6,418 times as UNDETERMINED. Oh, the inept NTSB also will hit the dead pilot up with poor pilot preflight or maybe carburetor ice…. when the real fault lies in the fuel tanks. HOW HAS THE FAA AND NTSB ALLOWED THIS LACK OF POSITIVE DETECTION IN THE FUEL TANKS OF THE CESSNA AIRCRAFT TO EXIST UNDETECTED FOR DECADES? LACK OF OVERSIGHT OR JUST PLAIN___________, YOU FILL IN THE BLANK. Whats makes a four cylinder, two plugs per cylinder, two magnetos, air, compression and UNCONTAMINATED FUEL engine run. Time for the NTSB to hire a few good old country boy’s to help figure out why the Cessna engines are sputtering to the ground.


    The ‘ green’ corn industry does not want us to know the damage and destruction the corrosive and energy deficient product can cause.
    I also uses more petrochemicals to produce than the energy result.

Leave a Reply

Your email address will not be published. Required fields are marked *