I am solo but like I said I just follow what my accountant says and suggested. and that is to keep track of the work mileage on my truck. I turn that in at tax time. mower fuel is just mixed in with all my expenses for the season. I used to save the receipts from the mowers but I don't any more. mowers are filled up with a diff card than my truck so I can track it that way if I need to.