As an incentive to the use of unleaded petrol, the 1988 budget reduced the excise duty on unleaded compared with leaded petrol. Subsequent reductions have resulted in a price differential now of 10p per gallon in favour of unleaded. This has been a significant factor in achieving an increased market share for unleaded, which by the end of December 1991 was over 27 per cent. The effect of regulations shortly to be made will be that, from the beginning of 1993, all new petrol engined vehicles will have to be capable of running on unleaded petrol.