California Code, Revenue and Taxation Code - RTC § 60122

The board or its authorized representative may issue a California fuel trip permit to interstate users for entry into this state. The California fuel trip permit shall be valid for four consecutive days and includes any reentry into the state during the four-day period. The fee for issuance of a California fuel trip permit is thirty dollars ($30). Other provisions of this article and Article 1 (commencing with Section 60201) of Chapter 6 shall not apply to the holder of a California fuel trip permit who uses only diesel fuel brought into this state in the fuel tank of the qualified motor vehicle and diesel fuel purchased in this state with the diesel fuel tax paid and delivered into the fuel tank of the qualified motor vehicle. Any diesel fuel tax paid to a diesel vendor for diesel fuel taken out of the state in the fuel tank of a qualified motor vehicle operated under a California fuel trip permit shall not be refunded to the holder of the California fuel trip permit, notwithstanding any other provision of this part.

The board may enter into an interagency agreement with the Department of Motor Vehicles providing for the issuance of California fuel trip permits by that department.