Okla. Stat. tit. 69, § 69-3018: Determination of fuel consumption

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: