Miss. Code Ann. § 27-61-23

In order to carry out the purpose of this chapter, the commission is hereby authorized and empowered to promulgate and enforce reasonable rules and regulations, and establish standards for the determination of the number of miles which a gallon of gasoline, diesel fuel, or kerosene would propel the different types and weights of vehicles. In order to carry out the purposes of this chapter, the commission is further authorized and empowered to determine and establish, from the best information obtainable, the average number of miles which each type or kind of fuel will propel each type or class of vehicle.