All-wheel-drive is safer in theory, because that distribution can get power to the wheels that have traction.

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ith the exception of sports cars, pickup trucks, and some truck-based SUVs, most cars these days are either front-wheel-drive or all-wheel-drive (the rest are rear-wheel drive). In many cases, all-wheel-drive is optional and presented as being a safer alternative in wet weather. But is it worth the extra money and added weight?

Before we answer that, we'll start with a primer. Front-wheel-drive means that the engine's power is transferred to the front wheels, and those wheels "drive" the car. In all-wheel-drive cars, either power is transferred to all wheels simultaneously, or a computer distributes power to each wheel and adjust that distribution when necessary, like when the pavement is wet or when one wheel is slipping. Four-wheel-drive systems are similar to all-wheel-drive, but are usually only active part of the time, often at the driver's discretion.

2013 Ford Fusion The 2013 Ford Fusion is available with all-wheel-drive.

All-wheel-drive is safer in theory, because that distribution can get power to the wheels that have traction, and because all-wheel-drive cars tend to be "neutral" when they lose grip. That means when the car slides, it doesn't fishtail or plow, making it easier to bring back under control.

By contrast, front-wheel-drive cars tend to understeer, or plow (by continuing on a straight path when the wheels are turned), when the front tires lose grip. Understeer is easier to control than oversteer, or fishtailing, which is more prevalent in rear-wheel-drive cars. When faced with understeer, it's generally best for the driver to do less of whatever he or she was doing. For example, if understeer is being caused by a driver using too much throttle, he or she should back off the gas.

Even though understeer is easier to control than oversteer, it's not as easy to deal with as a car that breaks loose neutrally. More importantly, all-wheel-drive cars are often more reticent to break loose, since power can be shifted to the wheels with the most grip.

Of course, the main advantage to all-wheel-drive is that it can offer more grip on wet pavement, especially in the case of systems that shift the power to the tire or tires with the most grip. Front-wheel-drive can't do that.

That doesn't mean all-wheel-drive is worth it, though. For buyers in the Midwest, the Northeast, and in other places where inclement weather is a frequent occurrence, it might be worth the extra coin. But for buyers in the South and other dry, warm-weather regions, it's hard to justify. Perhaps customers who plan on driving their cars hard could use it, but it seems wasteful otherwise.

2013 Cadillac XTS
The 2013 Cadillac XTS is also available with all-wheel-drive.

Unless you live in a place where it snows.

All-wheel-drive is sold as being better at handling snow, and it can pose an advantage there, again because of some systems' ability to shift power to the tires with the most traction. Even systems that don't shift power have an advantage, since all four tires are getting power. So we'd suggest that if you live in the snow, all-wheel-drive is worth it.

All-wheel-drive doesn't just add cost to the initial sticker price, it also adds weight and complexity. That means repairs could be more costly, and fuel economy will suffer to some degree, which will hurt at the pump. Buyers need to think about this before paying for the peace of mind that all-wheel-drive can offer.

Unless you're driving in inclement weather frequently, all-wheel drive just isn't worth the extra cost.