A Before and After Study of the Change to Unleaded Gasoline-Test Results from EPA and Other Cycles 900150

A fleet of 50, 1986-1987 model year cars designed for unleaded gasoline has been tested on the road and on a chassis dynamometer over 5 driving cycles and a wide range of other manoeuvres including steady speeds. It was found that the fuel consumption of this fleet was 17 to 23% (depending on test cycle) less than that of a corresponding fleet to leaded fuelled cars of 1980 model year average. Exhaust emissions were significantly lowered in the range of 45 to 93%. However trend line analysis of the several data sets indicates that the ULG fleet has about 6% higher fuel consumption than would have been expected if there had been a continuing evolution of leaded vehicle technology. The data base produced has applicability to a wide range of planning and design tasks, and those illustrated indicate the effects of speed limit changes and advisory speed signs on fuel consumption and emissions.

THE REDUCTION in fuel use by the Australian vehicle fleet brought about by the fuel consumption goals (similar to the CAFE in the U.S.) and the parity pricing of indigenous oil with Saudi Arabian light crude have been the major contributors in causing a significant change in the demand for crude oil. The growth rate in the demand has fallen from 4% per annum in 1978 to almost zero in 1985 and now is projected to run at 1% for the next few years. This turnaround in demand together with increased oil production led to Australia becoming an exporter of crude and, for a short time, to be self sufficient, although in general a net importer.

The ‘fuel consumption goals’ was a voluntary government-industry code set in terms of the U.S. practice of a 55:45 weighting of the EPA city:highway test cycles that called for a reduction of 20% in the national new-vehicle, average fleet fuel consumption (NAFC) from the 1978 value of 11.3 L/100 km by 1983 and the target of 30% (8 L/100 km) for 1987. In the event only a 16.5% reduction was achieved by 1983 to 9.4 L/100 km and the target for 1987 was re-negotiated to 8.5 L/100 km because of the change in exhaust emission standards from Australian Design Rule (ADR) 27A (U.S. 1973 standards) to ADR 37 (U.S. 1975 standards) in 1986 and the consequential change to unleaded gasoline (ULG) of 91-93 RON. As in the U.S. the resurgence in demand for slightly larger or more luxurious (heavier) cars is making substantial improvements in fuel use more difficult to achieve. Even by 1988 the NAFC had only been reduced to 9.1 L/100 km.

In common with U.S. experience drivers have reported (1)* that most often the fuel use achieved by their cars is worse than that published in the Federal Government's booklet called the Fuel Consumption Guide. Yet small errors in the projection of the growth or decline in the demand for gasoline can have a significant effect on national planning for fuel resources because over half the crude consumed is used as transport fuel. The change from a 4% growth (implying a doubling in demand in 18 years) to the near plateau in national oil demand, just identified, has contributed to the gloomy projections of the late 70's, of only 40% self sufficiency by the turn of the century being converted into the view of three year's ago of 80 to 90% self sufficiency. However, the fall in the price of oil to around $17 a barrel makes that projection look optimistic and self sufficiency at year 2000 may fall to about 50%.

Clearly, therefore, it is important to understand how the changes is vehicle fuel demand measured according to present practice will be realised in real world driving. Furthermore, through Department of Primary Industry and Energy programs there are strong efforts to reduce fuel demand by changing driving patterns through traffic engineering including road alterations and computer control of signals, which minimise stops as well as improving travel time. These actions have been proven to reduce fuel demand by 13% on a road network basis and by 20% along individual roads (2,3).