More oil is less gas in the fuel mixture. Lean is mean and makes power, but it burns pistons and carbons up exhaust systems. Fuel also cools the engine not oil.
Full synth. oil at 40:1 in any old motor will not hurt it. Old junk oils from back in the day, '60's - '70's where 20:1.
Modern oil, modern mixture.
I haven't hurt an antique motor yet running them on Klotz synth. oils at 40:1 with snowmobile engines and they are way more stressed than power tool engines. Use it in my old saws also, no smoke and no problems.