I was talking to someone that owns a small engine business. They had 6 chainsaws come in the other day. All of their problems were ethanol gas related.
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Ethanol: Death Sentence for 2 Stroke Engines
Ethanol Causes Lubrication Issues Between Oil & Engine
Ethanol Corrodes & Dissolves Various Plastic & Rubber Components
Ethanol Causes Hotter Operating Temperatures In 2-Strokes
Ethanol-blended Gas Has A Lower Fuel Economy Than Regular Gasoline
What Are Your Options For Working With Ethanol-based Gasoline?
https://www.fixyourdirtbike.com/tips...troke-engines/
Having shared all this, I doubt using premium gas would boost a Mirage's performance/mpg that drastically.
You may need to do the experiment for us? It's hard to keep all the other variables (wind, temperature, etc...) constant with an experiment like this, however.
I think some members have tried premium fuel, & I hope they speak up again.