I can get 100 octane Sonoco in town so I can run the test with that. I like I have a full tank so I'll run it low and put 5 gallons of the Sonoco in it.
I'd highly suggest getting it low & siphoning the rest out. it only takes 10% of ethanol (90% is still gas) to cause these issues so it wont take much (ethanol) percentage to invalidate your test and the refinery people I have spoken with say the percentage varies widely (up or down) from the nominal 10% and the oxygenated fuel these days is garbage (didn't have time to ask em why on the last Q). Holler how it turns out