I rent a car for uber. In nyc, thats over 400 a week. So I plan on deducting rental fees and gas instead of mileage. I only use the car for work, but how can i prove that? How can the IRS disprove it? I don't track mileage because i found i was just lumping all the days work into one "trip" "for business". The IRS takes our word about mileage classification, would they take my word if I said car is 100% business?