The cost effectiveness of changes to the power plant are examined. In 1979 diesel fuel represented 12.5% of the fuel consumed by road vehicles and 98% of light vehicles used petrol. The petrol/distillate ratio was 1.33 in 1979/80. A petrol/ distillate ratio change is not a cost-effective energy conservation strategy unless crude oil has a real value greater than $35/bbl for commercial vehicles. The value for cars is $100/bbl or the additional capital costs of $1000 must be equivalent to less than 9c/L of the fuel used per year. Some minor changes in fleet composition are indicated. The use of LPG fuel from indigenous sources is more cost effective than conversion to diesel power plants.