Notwithstanding the provisions of Section 8651, on or after January 1, 1966 the excise tax imposed upon liquefied petroleum gas shall be at the rate of six cents ($0.06) for each gallon of fuel used. All references in this code to Section 8651 shall be deemed, with respect to the rate imposed upon liquefied petroleum gas on or after January 1, 1966, to also refer to this section. Neither the tax imposed by this section nor the tax imposed by Section 8651 shall apply to the use of liquefied petroleum gas in a vehicle during any period of time for which the owner or operator of the vehicle has paid the annual flat rate fuel tax as provided in Section

8651.7.