All-wheel drive and four-wheel drive – is there really a difference?
Is it all-wheel drive (AWD) or four-wheel drive (4WD)? It seems logical that these terms can be used interchangeably. After all, if a car has four wheels and is four-wheel-drive, surely it’s an all-wheel-drive too? So is there a real difference?
As far as the names go, its highly subjective, so there’s no definitive difference. However, all-wheel-drive and four-wheel-drive can be used to differentiate between two distinct ways power is sent to all four wheels in most modern cars.
So what is four-wheel-drive?
Firstly, cars we’ll refer to here as four-wheel-drives send a constant stream of power to all four wheels. Although a basic differential system (the part that delivers power to the rear axle) is still used, modern technology means they’re much more refined and advanced than four-wheel-drives of the past.
An all-wheel-drive system sends power to only two wheels for the most part, and will only power all four if there’s a detectable loss of traction: in normal running conditions, an all-wheel-drive car sends almost all its power and torque to one axle.
All-wheel-drive’s capability is most noticeable in adverse weather, and is the drivetrain of choice for the latest performance models such as the Ford Focus RS and even the rear-engined Porsche 911 Carrera S – not a vehicle for off-roading by any means, but AWD does make it one of the best handling cars on the market, particularly in wet weather. AWD can thus be defined as a temporary or part-time system.
4WD vs AWD in the real world
Most of the time it can be hard to notice a difference between four-wheel-drive and all-wheel-drive on the road. Both deliver more grip than any two-wheel-drive car can muster, meaning they both handle corners and adverse conditions well.
The main difference between AWD and FWD is the amount of power and torque delivered to each wheel
The main difference between AWD and FWD is the amount of power (and torque) each wheel receives. With most 4WD systems, the torque (rotational energy created by the engine) delivered to each wheel is likely to be more evenly distributed than it is with an AWD system.
For example, 50/50 torque distribution means half the car’s power is dealt with by the front wheels, and half by the rear. In other words, each wheel gets 25% of the car’s power. This even distribution means 4WD is less prone to wheel slip and makes it the better choice for making slow, off-road progress. Torque distribution can vary, but for most driving conditions, 4WDs have no more than a 70/30 ratio.
This isn’t the case with all-wheel-drive cars which, most of the time, can be thought of as a two-wheel-drive. Under normal driving conditions, a Volkswagen Golf R will deliver almost all of its power and torque to the front axle. Throw it down a slippery lane however, sensors and a computer will deal with the loss of traction by sending more power to the wheels that need it most.
AWD produces fantastic road-holding ability in wet and icy conditions, as the car can correct any wheel slip instantaneously
This kind of system produces fantastic road-holding ability in wet and icy conditions, even if the car is travelling relatively fast – the fast-acting computers can deal with any wheel slip instantaneously. The handling benefits and a compact design means AWD tech is used in the latest high-performance models. Being light in weight means they can be used in supercars such as the McLaren 570S without any adverse affects too.
Which is the better system?
We can’t give you a definitive answer here, but it really depends what you’ll use the vehicle for. If you’re up muddy lanes and towing heavy trailers, a four-wheel-drive would be most suitable. If you want a car that’ll be as sure-footed in the wet as it is in the dry, or simply want one of the best-handling cars on the market, all-wheel-drive would be more for you.
If it were up to us, we’d probably take home the all-wheel-drive Skoda Octavia vRS – it’s the perfect half-way house. Fun and frugal (over 55mpg from the 2.0-litre turbo-diesel model), it’s also hugely practical and hugely capable thanks to its clever AWD system.