Re: Need advice on Oil mixture
The higher the octane number, the more compression the fuel can withstand before detonating - that's all it means. Ethanol is often used to raise the octane level of gasoline & the higher the octane rating is the more expensive the fuel is - as ethanol blended fuel phase separates (shelf life 30-60 days) & given that price for "premium", it's very likely that when you spend extra on that "better" fuel you are in actuality getting more ethanol not less & some amount of water mixed in for your troubles.
"stuck using 87 octane and had to change a top end shortly after doing that"
Interestingly this may have very little to do with a "clean burn" and more to do with the cleansing properties of ethanol - w/e the case if there's "crap in the gas" it's not the octane rating, it's time to find a different fuel station.