I'm probably getting too analytical here, but there are some other things to consider.
- Credit Card Rewards. I usually use my Citibank Professional card to buy gas. I receive 3 Thank You Points per dollar I spend on gas. 1 point is equal to 1 penny if I redeem for a $100 gift card, so for every $100 I spend on gas, I get $3 back.
- Mystery Shopping Reimbursements. At least half of my mystery shopping has been at gas stations, and nearly all of them include a gas purchase for which I am reimbursed. So often, my fuel cost is close to zero. This is significant since, at 8.9 cents per mile, gas is the highest vehicle expense I have. If I pay regular retail prices, 39.4% of my total vehicle cost is fuel.
- Tax Benefit. This gets convoluted since I no longer have wage income that I can offset with taxable losses (deducting mileage at $.50/mile lowers my income, thus lowering my tax liability). Still, for every mile that costs me 22.6 cents to drive, the IRS lets me deduct 50 cents from my tax liability. Works for me.