Field Experience with Smaller Cars

Because of the current interest in smaller cars, starting and warmup performance, emissions, fuel economy, acceleration performance, and frequency of maintenance data were studied for 17 “small” cars of Amoco Oil's 1974-75 test car fleet. These cars encompassed a broad range of domestic production and also included a car with a diesel engine and a car with a stratified-charge engine. Cold starting and warmup were less of a problem with the 1975 cars than with the 1974's. Gasoline volatility studies with three of the 1974 model cars showed that cold starting and warmup performance was markedly reduced when using fuels with high 10%, 50% and 90% evaporated temperatures. The diesel car could not be started below -9°C (15°F) on the road or -18°C (0°F) in chassis dynamometer studies, and ability to start was highly correlated with fuel cetane number. These cars, in general, met the prevailing emissions standards at 6440 km and the diesel and stratified-charge engine cars were outstanding in this respect. Although the 1974 and 1975 cars gave similar fuel consumption on a kilometers per liter basis, the heavier 1975's were more efficient on a kilogram-kilometers per liter basis. In this respect, the diesel car was best while the stratified-charge car was rather poor. Carburetors required frequent servicing, primarily chokes, and two cars required valve guide servicing due to excessive wear.