ASTM is not a testing house. They produce consensus standards. Consensus, by definition, is an imperfect solution arrived at by compromise in which no one loves the outcome, but everyone can grudgingly accept. This is the benchmark these days for how aviation standards are created.
When a company produces something to the ASTM standard, they self-certify they are compliant by conducting the consensus tests. The FAA does not oversee that process. ASTM does not oversee that process. The manufacturer does.
When a company decides the ASTM standard is imperfect, illogical, not applicable, or limiting, or the industry can’t even reach a consensus as is the case here, then any manufacturer is free to come up with a proprietary solution and follow the much harder path of obtaining an FAA approval. FAA runs them through the wringer, demanding battery upon battery of robust testing to examine every corner case and ensure the manufacturer’s product meets its proprietary specification under all foreseeable conditions, and that the product built to the specification has no unsafe characteristics. FAA reviews and approves all the test plans, oversees and witnesses the testing, reviews and approves the test reports. When they are satisfied, they give the manufacturer a design approval (STC).
Separately, the FAA then oversees the production quality process to ensure every drop of fuel made to the FAA approved specification conforms to the FAA approved requirements, and has the paperwork to prove it. Furthermore, if at any point the FAA decides the product has some unsafe characteristic or has not been produced to its FAA approved specifications, then they have the power of Airworthiness Directives to demand change, stop its use, halt its production, pull it from the market, you name it.
In other words, the FAA STC and production approval process is far more demanding and far more robust than something produced under a consensus standard with no one overseeing the quality but the manufacturer.
I’ll take “FAA approved” over “ASTM compliant” any day, all day.
As pilots and aircraft owners we should embrace this approach. The only people that want the ASTM way are the refiners and big oil because they don’t want to lose the lucrative GA fuel business they have a virtual monopoly over, and they don’t want the burden and ongoing obligation that comes from producing something under the watchful eye of the FAA.