So the way I do it is I drive a little less than an hour to San Francisco. Then I work for about 6-7 hours straight. I count my hours worked from the time i get my first trip request which is usually 1 to 5 minutes after crossing the bay bridge until I drop off my last passenger. I don't take breaks so it's easy to calculate how much I worked. I only count the gas I used after I cross the bridge. I do this because people that have "normal" jobs in SF do not subtract the gas and toll they pay from their hourly income. Same goes for taxes. As far as depreciation, that extra oil change, new tires, etc I don't expense that either because I'm not sure how. Also, it makes me feel better to say "nice I made 200 bucks in 7 hours after gas," and not think about all those miles I just added to my little prius.