According to the EPA, 59 percent of the new light-duty vehicles built for the US market in 2022 had all-wheel or four-wheel drive. Since 2017 it’s been the most common drivetrain in the country, ahead of front-wheel drive. Six in ten.

Now ask yourself how many of those six ever see a dirt road, a snowed-in driveway or a track day. AWD has become the most successful upsell in the American car business, and most of the people paying for it are buying insurance against a winter they could handle better with a set of tires.

That’s not because the technology is bad. It’s brilliant. It’s because it’s sold as essential to people who’ll never use it, and they pay for it at purchase, at the pump, at the tire shop and at the service desk.

Where it came from

Two answers in 1980

Here’s a piece of trivia most Americans don’t know: the US and Europe both brought four-wheel drive to ordinary passenger cars at almost the same moment, and they did it for opposite reasons.

For the 1980 model year, American Motors launched the Eagle, a Concord sedan and wagon raised up and fitted with permanent four-wheel drive. Its transfer case used a viscous coupling, a sealed unit full of thick silicone fluid that let the front and rear axles turn at slightly different speeds in normal driving and stiffened to lock them together when one started to slip. It was nearly all mechanical and decades ahead of its time. Many people now call it the first crossover. It was built for snow-belt families, not for winning anything.

The hardware came from Jeep, which AMC owned at the time: the Eagle’s system was a modified version of Jeep’s Quadra-Trac, reworked by the British engineering firm FF Developments, which had been putting four-wheel drive into road cars since the Jensen FF of the 1960s. So the first American AWD family car carried a Jeep drivetrain refined by the same people who built four-wheel drive for a British grand tourer. Nobody at AMC was thinking about lap times. They were thinking about Buffalo in January, and they were right that buyers would pay for it. They just got there a generation before the rest of the industry noticed.

In March 1980, Audi showed the Quattro at the Geneva show. The FIA had opened rallying to four-wheel drive in 1979, and Audi walked straight through that door. Conventional wisdom said AWD was too heavy and too complicated for racing. Audi won the manufacturers’ title in 1982 and 1984, and Hannu Mikkola and Stig Blomqvist took the drivers’ crowns in 1983 and 1984. The idea itself came from testing a Volkswagen military off-roader in the snow, the Iltis, and the whole family tree is in our Audi quattro history.

One thing that usually gets mangled: the original Quattro didn’t have a Torsen differential. It had an open center differential the driver locked with a switch on the dash. The Torsen arrived with the Audi 80 quattro in late 1986 and then on the road-going Quattro.

The rally decade

The advantage was physics, not advertising. With power going to all four wheels, a car could come out of a gravel corner at full throttle while the rear-drive cars waited to straighten up. Lancia answered with the Delta HF 4WD and its Integrale evolutions and won six straight manufacturers’ titles from 1987 to 1992. We made the case for it as the greatest rally car ever built. Toyota’s Celica GT-Four carried Carlos Sainz to the 1990 and 1992 drivers’ titles, a car with a scandal of its own. Then came the Subaru Impreza and the Mitsubishi Lancer Evolution.

All of them needed AWD to win. That’s the point. It was developed to put big power down on bad surfaces, then sold in street versions to people who knew exactly what it was for.

How Subaru turned a drivetrain into an identity

No brand sold AWD to Americans like Subaru. It made symmetrical all-wheel drive standard across nearly the entire lineup and built its image around snowy trailheads, dogs in the cargo area and the people who own them. It worked. But even Subaru’s system isn’t one system. Manual-transmission cars use a viscous center coupling with a 50:50 split. CVT cars use an electronically controlled multi-plate clutch that defaults to 60 percent front and 40 rear. The WRX STI added a center differential the driver could adjust. Good engineering, but not the single magic mechanism the commercials imply. If you want to know why it’s tied to the flat-four, read about the Subaru boxer engine.

The three kinds of AWD you can actually buy

Permanent, with a center differential

A differential lets two wheels, or two axles, turn at different speeds. You need that because in a turn each wheel travels a different distance. A permanent system adds a third differential in the middle, between the front and rear axles. Audi’s Torsen is a gear-type center diff that sends torque toward the axle with more grip without any electronics. Early versions ran 50:50 in normal driving and could send 75 to 80 percent to one end if the other slipped.

It’s tough and doesn’t depend on sensors. It’s also heavier and always turning all four wheels, which costs a little friction and fuel. Audi has changed systems several times since, including a crown-gear differential from 2010 and "quattro ultra," which uses clutches to disconnect the rear axle. Check which one a specific car actually has.

On-demand, with a clutch

The car is front-wheel drive most of the time. When the front tires start to slip, or the computer predicts they will, a multi-plate clutch connects the rear axle. Haldex is the best-known name, used in VW 4Motion and transverse-engine Audis like the A3, TT and Q3, and similar systems sit under most compact crossovers sold in the US.

It’s lighter and more efficient than a permanent system. Its weak point is maintenance. The clutch and pump run in their own fluid, and VW specialists recommend changing it every three years or about 18,000 miles, cleaning the pump strainer while they’re at it. Plenty of owners never have. When the pump quits, the car just keeps going as a front-driver, and many don’t notice until the snow comes.

Electronic, predictive

BMW xDrive, Mercedes 4Matic and most premium crossovers use computer-controlled clutches, wheel-speed sensors and software that decides many times a second where the torque goes, often before a wheel slips. On a high-powered car, nothing works better. They also add sensors, actuators, wiring and software, and when a part fails it’s usually replaced, not repaired, with diagnostics tied to the dealer’s equipment.

What the window sticker leaves out

It costs fuel

More weight and more spinning parts. Take the government’s own numbers: the 2024 Toyota RAV4 in its base gas version is rated at 30 mpg combined with front-wheel drive and 29 with AWD. One mpg doesn’t sound like much. You’ll pay it on every tank for as long as you own the car, and on some models with permanent systems the gap is wider.

Tires become a set, not four tires

On an AWD car, the four tires need to match and wear evenly. If one is noticeably bigger in diameter because it’s new and the others are worn, the system reads it as a wheel spinning faster than the rest and the clutch or differential works constantly. That’s why automakers and tire retailers tell you to keep all four matched. An unrepairable flat halfway through a set’s life can turn into buying more than one tire.

More parts to fail

A front-driver has an engine, a transmission and a differential. AWD adds, depending on the system, a transfer case, a center differential or coupling, a driveshaft, a rear differential, rear axle shafts and CV joints, sensors and a control module. More fluids, more seals and more things that can leak or break.

And it doesn’t stop you any faster

This is the big lie by omission. AWD helps you get going and accelerate when grip is low. It does nothing for braking and very little for cornering. Tire Rack and other testers keep showing the same thing: in snow and ice, the tires make the difference in stopping distance, not how many wheels are driven. A front-drive car on winter tires stops better than an AWD crossover on all-seasons. AWD on the wrong tires just gets you to the place where you can’t stop a little sooner.

Who actually needs it

You live in the mountains or the snow belt and drive in it daily. If your commute climbs a pass that’s snow-covered much of the winter, it makes sense. With proper winter tires.

You really go off-road. Not the gravel lot at the trailhead. Washed-out forest roads, ruts and creek crossings. And there you want a low range, which most crossovers don’t have. A body-on-frame truck or a small 4×4 like a Jimny or the old Suzuki Samurai will go places a $60,000 crossover won’t.

You have serious horsepower and use it. Past a certain output, two tires can’t put it all down without spinning. If it’s a 600-hp sedan that only sees the interstate, you don’t count.

You tow in tough conditions. Weight behind you, an incline and poor grip: that’s where 4×4 earns its keep.

You don’t need it if your car goes from the garage to the office parking lot, if you head to the mountains twice a winter, if you want a crossover because it sits higher, or if you just like how "quattro" or "xDrive" looks on the tailgate. A front-drive crossover on good tires will do everything you actually ask of it.

If you really need it

Know which system you’re buying, find out how it’s maintained and do the maintenance. For real trails, buy something with a low range. For snow, buy the tires first and the drivetrain second. For a family hybrid, Toyota’s AWD-i uses an electric motor on the rear axle with no driveshaft at all, which removes a lot of the mechanical parts that can fail.

Sounding good isn’t the same as being good

The Quattro, the Delta, the Celica and the Impreza had AWD because without it they didn’t win. Every part had a job and every extra pound was paid back in speed.

Today it’s a badge. "Quattro" sounds premium, "xDrive" sounds high-tech, "4Matic" sounds safe. If you need it, buy it with your eyes open. If you don’t, spend that money on four good tires, the only thing that actually holds your car to the road.

Photos: Przemysław Jahr (public domain); Kev22 (CC BY-SA 4.0); Andrew-44-19 (CC BY-SA 4.0); Brian Snelson (CC BY 2.0); Jakub Hałun (CC BY-SA 4.0). Via Wikimedia Commons.

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