Premium Octane?

[Big TP]

Its not what you think.....this mornings price at my local store: $2.93 for 87 octane unleaded and $3.47 for 91 octane ethanol free premium. If you do the math and use a 6 gallon fill up, it will cost you $17.58 for regular and $20.82 for premium. If I get 41 mpg on unleaded, I'll get a 246 mile ride for my 6 gallons. For the same 6 gallons, I'll get 264 miles at 44 mpg for the premium. Break it down to the per mile fuel cost and it costs me $0.1399 per mile for unleaded and $0.1268 per mile for premium so.....Its cheaper for me to run the premium, get better mileage and what I perceive as better performance.

I may be wrong but looking at your numbers it seems you spent $.3.24 more on the Premium fill up and got 18 more miles?
If that's right than the 87 octane would be cost efficient, of course not taking into account perceived performance improvements.
Most Respectfully,
TP