Any person who operates a motor vehicle that is equipped to use motor-vehicle fuel and LP-gas interchangeably is presumed to have used LP-gas exclusively in the operation of said vehicle unless proof of the amount of motor-vehicle fuel used is maintained in such form as the director may reasonably require.

L. 1959, ch. 405, § 5; L. 1973, ch. 402, § 10; July 1.