I'll email you my spreadsheet if you want.

Maybe I have the mixing of the torco wrong. Somewhere, I read that it took one full can of torco to boost 1/4 tank of 93 octane to 106. I assumed that a "tank" was 20 gal, so 1/4 tank was 5 gal, and that torco cost $14/can.

I then assumed that Xylene cost $4/gal, and is 117 octane.

My target was to boost 91 (what we get her in tucson) to 93.

For a 15.9 gal tank, it takes 14.7 gal of 91 plus 1.2 gal of xylene to yield 93 octane. The total tank cost assuming $1.80/gal premium 91 is $31.30.

If it takes 0.25 gal of torco to boost 5 gal of 93 to 106, then the effective "octane" of the torco is about 350. This will all work if the amount of torco you use is linear, meaning you get half the octane boost if you use half as much torco.

I find that I will need 0.12 gal of torco (about half a can) to raise 91 to 93. If torco is $14/can, then the cost of the tank is $35.26.

All these calculations were done with a spreadsheet I wrote.

Torco would have to cost $7 a can for it to be the same price as xylene per tank, if I have the mix ratio right.

If I have that wrong, then please tell me what the right mixing is, meaning how much torco boosts what octane gas to what new octane? Then I can re-calculate the cost.