What is the difference between all-wheel-drive (AWD) and front-wheel drive (FWD)?
The main difference is where the engine sends power. In FWD vehicles, the engine only powers the front axle, whereas, in AWD vehicles, the engine powers both front and rear axles.
Here's a brief rundown on the four types of wheel drive systems:
Front-Wheel-Drive: The vast majority of new cars on the road today are front-wheel drive vehicles, including almost all models of SUVs. Front-wheel drive SUVs come equipped with additional parts that automatically route some of the engine's power to the rear axle when necessary. Since the drivetrain is positioned in the front and pulls the weight of the vehicle, the effect of oversteer (rear end of the vehicle sliding out and causing a tighter turn than intended) is limited. FWD cars are good at climbing hills and perform well in slippery conditions. From a manufacturer's standpoint, FWD vehicles are beneficial because they are cheaper to manufacture and use space more efficiently.
Rear-Wheel-Drive: Rear-drive systems are usually found in sports cars, pickup trucks, older truck-based SUVs and luxury high-performance sedans. It is a two-wheel drive system that pushes the car from the rear axle. Rear-wheel drive systems (RWD) enable better handling in performance cars by distributing weight more evenly. Also, since the front wheels aren't in charge of both steering and powering the vehicle, makers of rear-wheel-drive vehicles are free to tune the suspension system for handling superiority. These days, most performance RWD cars typically have AWD options available as well. RWD trucks are made with robust and heavy parts that provide better traction when hauling a heavy load. RWD vehicles have inferior traction control when road conditions are slippery, however.
All-Wheel-Drive: AWD systems deliver power to each corner of the vehicle, similar to 4WD cars. However, unlike 4WD cars, AWD is always engaged and provides varying amounts of power to the axles depending on traction conditions. All-wheel drive systems primarily power one set of axles, either front or rear. When the car feels traction loss in one axle, it will automatically divert more power to the other axle to compensate. Not all AWD systems utilize the same power ratio. For example, Subaru's all-wheel-drive system continuously sends at least 20% of the engines power output to the rear axle, with the possibility of directing more if necessary. Other systems exclusively power the front axle and only rebalance engine output to the rear when the front tires are losing traction.
AWD cars work well in moderate off-road driving situations, or when driving conditions are prone to change due to terrain variation or volatile weather conditions. In addition, AWD vehicles provide great overall traction during acceleration due to all four wheels being engaged. AWD systems are commonly found in car-based SUVs and minivans, but also often make an appearance as an option for performance rear-wheel-drive cars.
Four-Wheel Drive: Four-wheel drive (4WD) cars are generally tuned for extreme off-road uses like traversing over deep water, scaling boulders or climbing steep hills with poor surface traction. When enabled, 4WD systems send power to all four wheels using front and rear differentials plus a transfer case that distributes power equally regardless of traction. In addition, some 4WD have two gear ranges, high and low. The low gear range proves especially helpful when low-speed climbing power is required. There are three different mode toggle options in modern four-wheel drive vehicles. Full-time systems are always engaged, automatic systems switch between 2WD and 4WD automatically, and part-time systems require the driver to switch between two-wheel drive and four-wheel drive modes manually. Driving a part-time 4WD vehicle on the pavement with 4WD enabled can cause damage to the vehicle's drivetrain.
Is an All-Wheel-Drive or Four-Wheel-Drive vehicle worth it?
It depends on the driving conditions you plan to encounter. Two-wheel-drive cars handle rain and light snowfall just fine, with front-wheel-drive cars generally eking out rear-wheel cars in safety. Rear-wheel-drive cars excel when performance is critical (although all-wheel-drive systems can provide more traction). All-wheel drive vehicles are great for light off-road driving and typical snow conditions. If you're powering through heavy snow or tackling extreme off-road terrain, a four-wheel-drive vehicle with high ground clearance and a low gear range is the set of wheels you should be looking for.
In addition to weather and terrain conditions, fuel efficiency is another factor that should be considered. Both four-wheel-drive and all-wheel-drive systems contribute substantial heft to the vehicle, so you end up trading efficient fuel economy for that extra traction. And sending power to all four wheels when it isn't necessary also contributes to more drag and reduced efficiency. Some all-wheel-drive systems now automatically disconnect power going to the rear axle when the system determines the front two have sufficient traction.
Traversing Winter Terrain
Safety and handling is another concern. Many potential car buyers view all-wheel drive and four-wheel drive SUVs as safer due to the increased traction they provide. However, that straight traction contributes absolutely nothing to assist in safer turning or braking, especially when ice is a factor. Sure, the robust traction is helpful when you need to get going, but stopping is another story. Four-wheel drive and all-wheel drive cars are involved in icier condition-related accidents than their lighter two-wheel drive counterparts, and their drivers' misconceptions about the limitations of their 4WD and AWD drivetrains certainly plays a part. Even on dry streets, heavier four-wheel-drive and all-wheel-drive vehicles require more distance to come to a complete halt.
When driving through winter weather, you can't go wrong with a set of winter tires. Numerous independent studies have shown that good tires play the largest part in determining a vehicle's safety performance when driving through snow and ice. That is because snow tires are made from a softer kind of rubber than standard tires. Their more pliable texture enables superior traction when the temperature drops. Besides, winter tires feature specialized treads that are designed to carve into the snow and eject it out of the way. Snow tires are embossed with a three-peak mountain and snowflake logo, so it's easy to see if the tire you're looking at passes snow performance standards and is rated for winter driving.
To Sum it Up:
If you are mainly looking to drive in the city, a two-wheel drive car is all you need. Throw a set of winter tires on when going through light snowfall and it will perform fine. This is the cheapest option, since all-wheel drive vehicles are more expensive right out of the dealer and less fuel efficient, leading to increased expenses down the line. A front-wheel drive vehicle is more versatile and less prone to oversteer. If you live in a warm, dry climate and are a performance enthusiast, a rear-wheel-drive car might be right for you.
When you want a mix of urban driving and rural performance, nothing beats the versatility of an all-wheel-drive vehicle. All-wheel-drive cars are jacks-of-all-trades and can weather harsh winter conditions when equipped with a good set of snow tires. All-wheel drive cars also redistribute power automatically, so you don't have to worry about fumbling with controls and can focus on the road.
For heavy high incline off-roading and trudging through unplowed roads, a four-wheel drive car with a low gear range and high clearance provides the best mobility. Just remember to enable the right settings for the terrain, as failing to do so can damage your drivetrain.