I do all of that with Excel. One sheet for mileage, another for maintenance, another for "expendables" like tires and lamps, with a master screen that puts all the costs together. It's not a lot of work to put together such a workbook, and the math is really trivial. A nicely polished app that does all that for you and has you simply enter the data would be very nice, but I'm not chomping at the bit to buy anything like that at the moment.