same as getting it certificated to use that fuel. Certification
testing covers a wide range of conditions that some aircraft may never
see but must be addressed if we are going to let Type certificated
aircraft use the fuel. Remember an STC for a fuel would allow that
aircraft to fly with paying passengers at night, IFR in bad weather, in
the most extreme conditions e.g. Alaskan winter or Saharan Summer, so
the STC tests must cover all know operating conditions.
Earl Lawrence

You mention 10% alcohol, what about 5.7% alcohol as is required in
California Fuels?