Jay Honeck wrote:
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Few planes have fiberglass tip tanks -- so I think his experience is a
fairly valid test for many aircraft owners. It seems to be "running"
just fine in his low-compression Lycoming O-540, which is exactly what
you might expect from an old 1940's-era tractor engine.

Ethanol based fuels aren't entirely friendly to aluminum either, which
is one of the reasons the STC forbids it.