42-5166. Diesel fuel imported and used by locomotives; exemption A. The tax imposed by this article does not apply to diesel fuel imported in the fuel tank or tanks of a locomotive and consumed in this state. B. Diesel fuel imported and consumed in a quantity exceeding the capacity of the fuel tank or tanks of a locomotive according to the manufacturer's specifications is subject to the use tax imposed by this article. The use and consumption of the fuel shall be reported and the tax shall be paid in the manner prescribed in section 42-5162.
Arizona Legal Code