a letter to my boss's boss!

i thought the letter was fine, other than the following:

even if you’re buying premium, $.40/mile should more than cover your gas expenses. i know your mileage will vary, but at $3.50/gallon, it costs me about 12-13 cents in gasoline to drive a mile. If I bumped it up to premium and knocked a few mpg off, it might go up a nickel or dime, but at $.40/mile AND 93 octane, you’d have to get less than 9 mpg to be losing money on gasoline.