An experimental study was undertaken to determine the influence of fuel octane quality, engine compression ratio, and ignition timing adjustment on fuel utilization efficiency. This information, combined with data on refinery energy consumption for producing fuel of various octane qualities, can be used to estimate the potential for improvement in miles traveled per barrel of crude oil consumed.
The vehicle selected for this investigation incorporated a closed-loop, air/fuel ratio control system using an oxygen sensor and a three-way catalyst. Ignition timing was adjusted for minimum fuel consumption at each of three compression ratios with the engine operating on fuels of various octane quality. An ignition timing retard system was used for those combinations of compression ratio and fuel quality which precluded use of best ignition timing.
Results indicate that a 13% improvement in miles traveled per barrel of crude oil consumed is possible.