AWD Vs. 4WD in Gas Mileageby Jeb Hoge
All-wheel drive (AWD) and four-wheel drive (4WD) perform similar functions in different vehicle types, but in some ways operate quite differently. Gas mileage depends on the design of the vehicle.
AWD is a system where all four wheels are always being powered, but are able to rotate at different speeds and with torque being sent to whichever wheels have traction. This is the type of system most commonly used in passenger cars and light sport utility vehicles (SUVs) or family haulers.
4WD is usually implemented as a part-time system. The vehicle in most on-road conditions only uses two-wheel drive, unless the driver chooses to engage the transmission's transfer case and "lock" in four-wheel drive. This is used for pickup trucks, heavy SUVs and off-road vehicles like the Jeep Wrangler.
In truth, the type of drive system (4WD vs. AWD) has less to do with differences in fuel economy than other factors in the design of the vehicle. 4WD vehicles often are larger and heavier and they have bigger engines and heavier-duty transmissions than AWD vehicles, all of which negatively affect fuel economy for 4WD vehicles.
AWD is usually for on-road or light off-road use only and is designed more to help maintain traction in wet or slippery conditions than in tough off-road conditions. Pick AWD if your concern is for driving safety and performance.
4WD systems are better suited for off-road use because they are designed to drive all wheels at the same speed and can often multiply engine output using low gearing that would not be used for most on-road driving. However, for off-road use or towing, these characteristics are very desirable.
Another Way to Save Fuel
Consider a front-wheel-drive (FWD) vehicle with traction and stability control systems rather than 4WD or AWD. In most situations, a modern FWD vehicle can be driven as safely as any AWD/4WD and will yield better fuel economy because of lighter weight and less complexity.
Jeb Hoge has a degree in English and more than 10 years of experience as a technical/business writer supporting federal defense contractors and government agencies. He is a member of the Society of Technical Communicators and Toastmasters.