I contemplated something like that 20+ years ago, but also saw that there was at...

I contemplated something like that 20+ years ago, but also saw that there was at least one option with a small 4 cylinder engine that was reportedly quieter and able to run on straight unleaded IIRC.

Edit: a quick search shows those still available in 38, 49 and 79 cc models depending on the power needed. 100-150 mpg