As a mystery shopper I have to be aware of my costs. Depreciation is the cost of using my car in a given time period. Instead of expressing the cost of my car as a one-time expense when I bought it, I spread out the cost of my car over its expected life. Depreciation does not include other vehicle-related costs like gas, maintenance or insurance. I separate those out and report them as they occur.
I determined that each mile I drive costs me $.0867 in depreciation. I ended July with 31,389 and at the end of August there were 35,152 miles on the odometer. I drove 3,763 miles. For August, my vehicle depreciation expense was $326.25.