In determining the amount of motor fuel consumed each month, the Oklahoma Tax Commission shall divide the total miles traveled on the toll expressways by passenger automobiles, single unit trucks, and combination trucks and buses as certified each month by the trust, by the average number of miles per gallon of motor fuel consumed by each of those classes of motor vehicles. For the purpose of this section, the Oklahoma Tax Commission shall use the following rates for motor fuel consumed:
Added by Laws 1971, c. 333, § 18, emerg. eff. June 16, 1971.