Estimated speed/fuel consumption relationships for a large sample of cars

Speed-fuel consumption relationships were estimated using data on 350 1965–77 model year automobiles collected by Consumer Reports magazine. Three functional forms relating fuel consumption to speed were estimated and a summary with descriptive statistics was also computed. The results show considerable sensitivity of fuel-consumption rates to speed. Average decreases in fuel economy for all cars in the sample were 8% from 64 to 80 km/hr, 12% from 80 to 97 km/hr, and 13% from 97 to 113 km/hr. Sensitivity of the fuel consumption rates to speed increased with increasing speed and decreasing engine Size.