Last month I started tracking vehicle depreciation in my monthly expenses. At the end of April my odometer showed 18,860 miles. I ended May with 23,129 miles.
Each mile costs $.0867 in depreciation, and I drove 4,269 miles. For May, my vehicle depreciation expense was $370.12.
Depreciation is a significant expense for mystery shoppers. I drive thousands of miles every month and more than 90% (and probably very close to 100%) of my driving is for shopping. One side advantage to mystery shopping is that a lot of the errands most people have become "jobs" for me: grocery shopping, getting gas, buying household supplies, etc. The few errands I do have can usually be done along my daily shopping route.