Regular and premium gasoline have the same components, just in slightly different proportions. They mix quickly in the car's gas tank. 90.8 AKI will not affect performance.
Yeah, I track my correction factors (K). From this I can adjust the K in the secret instrument cluster menu. I do this about annually. The absolute values of the average of my K's for the last four fill-ups for both of our BMW's are less than 0.1%.
I hate waiting to buy gas. I use two local gas stations. One has eight pumps, and I'm usually the only one there buying gas. The other station has 32 pumps. I've found that Pump #23 gives away free gas, maybe 0.4%.
Gas station-convenience stores are pretty much the only place where the dregs of society and I cross paths. For this reason, I'm usually armed when I buy gas. The thresholds for using deadly force in Floriduh's self-defense laws are pretty damn low, actually hilariously low. Raptor Boy would do well to stay in his truck and leave me alone.
As soon as I pull up to the pump, and sometimes when I'm across the street at Sam's Club, I calculate how much 93 AKI and 87 AKI gasoline I'll need. It takes me one minute to reset the pump for the 87 AKI. Saving $4.50/tank, that works out to $270/hour for my time.
Gas Whispering, like Tire Whispering, works. Gas Whispering will save about $1000 over 100k miles.
Before Gas Whispering and Tire Whispering, there was Oil Whispering. I read about the advantages of synthetic oil back in April 1976.
Popular Science - Google Books
The Putzer cars in 1976 were either sludged up or leaking oil. So, I didn't start using synthetic oil until 1985 (when Mobil 1 came with 5W-30). I got tired of giving the "Putzer Synthetic Oil Speech" to people. So, I made... wait for it... a spreadsheet. It takes all the variables and calculates the extended oil change interval to "break even" on cost, and then calculates the cost savings from a further extended oil change interval. A conservative estimate of MPG gain is about 2%.
Back in the bad old days of conventional oil, 4000-mile oil change intervals were common and prudent. (Frau Putzer brough a five-year-old, 25k-mile Honda Civic to the marriage, and the engine had varnish with supposedly 3000-mile oil changes with conventional oil.)
One of the variables is the cost of the owner's time either doing an oil change or getting an oil change done. When I was working, my time was worth $50/hour. I was on super-gliding-flex time, and I changed my oil at work in about an hour (but off the clock). So, it was reasonable to add that $50 in as one of the variables.
Throwing all the variables into the Oil Whispering spreadsheet, switching to synthetic oil and extending the drain interval from 4000 miles to 7500 miles would save on the order of $70 (over 7500 miles). Over 100k miles, the savings would be on the order of $1000. Less engine wear and no engine deposits are qualitative benefits.
The Oil Whispering spreadsheet would convince even my electrical engineer friends to start using synthetic oil.
Most new cars now require synthetic oil. So, the Oil Whispering spreadsheet is now pretty much moot. But, back in the day, it'd save my friends $1000 over 100k miles.