The terms we are missing here are variable and fixed. Many of the costs of owning a vehicle are fixed: insurance, taxes, registration, inspection, licensing (for the driver) and the portion of depreciation due to age. The rest are variable: gas, oil, tires, and the depreciation due to mileage. If you are already incurring the fixed costs of ownership, the additional incremental variable costs of an additional trip are relatively low, probably around $.10-.20 per mile for a reasonably efficient vehicle.