Full Time 4 Wheel Drive Full time four-wheel drive systems bring the best of 4WD and AWD together because the system uses technology from both. Since AWD passenger cars do not do heavy off-roading, the added strength and technology used in the full time systems is not needed and has not been made available. Some cars have been manufactured with part time 4WD yet had no fuel mileage increase over the AWD's. Part time four-wheel drive systems are popular due to their design simplicity and increased fuel mileage due to fewer moving parts while in the 2WD mode. Owners of vehicles equipped with these systems need to be informed about their proper operation in an effort to eliminate damage caused by improper use.
Manufactures provide maintenance and use information in the owner's manual.
Decrease in fuel mileage is the trade off with added maintenance expense should the system break down.