PC-electricity saver was effective and reliable, but it was not economical yet. Since the price of these devices are so expensive comparing with electricity saving. The pay-back period was calculated 9 to 15 years roughly. Chassis dynamometer tests show the fuel economy changes between 1.8% deterioration to 1.8% improvement, and monitoring tests show little changes in vehicle performance with these devices. Finally, it was concluded that there are little effects of the vehicle fuel economizers on vehicle fuel economy in the present test results. (author). refs., figs., tabs.