County commissioners shall be allowed their actual and necessary maintenance expenses, together with such mileage as shall be determined by resolution of the board of county commissioners of the county or as provided by the charter of a home rule county, within the limits provided under section 30-11-107(1)(t), for each mile actually traveled whether within or without the state when engaged in business on behalf of the county; but no mileage expense shall be allowed while said commissioners are traveling in an automobile furnished by the county.
C.R.S. § 30-2-103