HC Deb 07 April 1959 vol 603 c51

I propose, also, to make certain very minor changes in the scope of the duty on heavy oils used in road vehicles so that in future oil used in a subsidiary engine mounted on a vehicle will not be chargeable with duty, and, also, that only those vehicles which use the roads to an extent which makes them licensable as road vehicles will have to use dutiable oils. Details will be found in the White Paper. The effect on the Revenue will be negligible.