There is hereby levied an excise tax of fifteen and one-half cents per gallon on all gasoline or special fuel, which tax shall be computed in accordance with the appropriate measure of tax as prescribed in this article: Provided, That beginning the first day of May, one thousand nine hundred ninety-three, the tax levied by this article is twenty and one-half cents per gallon: Provided, however, That on and after the first day of August, two thousand seven, the tax levied by this article is fifteen and one-half cents per gallon.
W. Va. Code § 11-14-3