“93 otate premium is $.50 over 87 oxy where I live...”
Ethanol gas typically delivers 15% less MPG.
Factor that into the price of your 87...
I only use 91 octane (highest grade we get - it’s 93 but we’re at 5,000 feet so it’s rated lower) and am very happy.
Straight premium is all I use in my pontoon boat, lawn mower and other small engines.