TOKYO -- Vehicle fuel efficiency is said to decrease by about 30% in cold areas during winter compared to summer. The Mainichi Shimbun looked into tips to improve fuel efficiency to ease the burden on household budgets as gasoline prices remain high in Japan.

The national average retail price for regular gasoline was at 184.4 yen ($1.24) per liter as of Feb. 17. Gasoline evaporates less easily at low temperatures, causing an increase in fuel injection and poor fuel efficiency. Additionally, the use of studless snow tires made from soft rubber increases resistance from the road surface, which can further reduce fuel efficiency.

According to the automotive goods chain Yellow Hat Ltd., effective measures to improve fuel efficiency include removing unnecessary luggage to lighten the car, increasing tire pressure and adjusting the way the accelerator is pressed to maintain a constant speed while driving.

A study by the Japan Automobile Federation showed that using an adaptive cruise control system, which automatically adjusts the vehicle speed to maintain a safe following distance, improved fuel efficiency by as much as 12% in some cases.

Moreover, the automotive air conditioning system can be used in a way that helps save fuel during winter. According to Zurich Insurance Company Ltd., the A/C button in gasoline vehicles only controls the cooling and dehumidification functions. The air compressor runs and blows cool air when the system is turned on, and turning it off activates the fan mode. Since the compressor is powered by the engine, cooling the car places an additional strain on the engine, decreasing fuel efficiency.

On the other hand, a car heater reuses the heat from the engine. The engine becomes hot while driving and is regulated by coolant, and the heat from this coolant is utilized for keeping passengers warm. It is unnecessary to activate the compressor for heating, so one can turn off the A/C if they just want to stay warm.

Turning off the A/C can help save gasoline. According to the Ministry of the Environment, when the car's interior temperature was set to maintain the same 25 degrees Celsius as the outside air, fuel efficiency worsened by about 12% when the A/C was left on, compared to when it was turned off.

However, as the A/C also has a dehumidifying function, it is better to turn it on even during winter to clear fog from the windows.

(Japanese original by Yuko Shimada, Business News Department)