While it's true that these low compression engines don't require high octane fuel, that they may even run worse... there's other, perhaps less obvious problems with the so-called "premium", issues that are somewhat regional & are consequences of both ethanol and the high cost of fuel.
Ethanol is a solvent and
has a very limited "shelf life" due to it's nature. As a solvent, contaminants in fuel are at an all time high. While there's often been concerns stated regarding the deterioration of the elastomers (rubber-like parts) like the seals and other components of our
fuel systems, the "fuel lines, gaskets, 'O' rings, etc" previously mentioned, remember that the fuel has been in storage before you purchased it and it's been having it's effect on the station's
tanks, lines and gaskets.
There's also the phase separation issue, water & alcohol mix quite easily whereas water and gasoline does not, if enough water is introduced into the fuel through exposure and time (condensation & even ambient humidity) the water will be drawn into the ethanol and the mixture will separate from the gasoline, forming a layer at the bottom of the tank, leaving three very distinct layers - the top being mostly low octane fuel as the octane number had been raised by blending in ethanol (and it's likely the higher the octane rating, the more ethanol had been added), the middle being mostly water with some alcohol and the very bottom the sludge created from it's solvent properties - and bear in mind that the pumps don't draw fuel from the top
of the tanks.
These effects are bad enough, but what makes them worse is few to no gas stations ever bother to clean their tanks let alone upgrade their pumps to compensate for the alcohol content, and with the cost of fuel - many folks don't buy the quantities of the higher octane "premium" that would be needed to ensure what you're getting is clean, "fresh" fuel, it's likely to have been sitting in that tank for far too long.
Remember, the advised "shelf life" of an ethanol blend by the time you get it is only about 2-4 weeks, but that's depending on how long it sat in storage & exposure, which you can't know except for the obvious, and that's the "cheap stuff" sells far more than the "premium" ...how long did the "premium 93 octane" sit in the gas station's tanks, dissolving years of varnish and phase separating? Is it really even close to "93 octane" anymore? Is it worth what you're paying? What are you really getting for your money?
*shrug* No way to really tell as it does depend on regional variables, but I do know this - I built myself a custom tank, obviously new and spotless I get my fuel from only the one gas station and despite the fact I buy the most popular "cheap stuff" which is clearly the freshest, newest fuel available with the tanker truck refilling the underground tank at least once a month, that once spotless tank of mine now has a layer of black, slightly gooey sludge that bears a remarkable resemblance to what dissolved pump hose would look like, after only one summer of riding...
Some "fuel" for thought lol