If you’re in the market for a new vehicle, you’re likely to see lots of car and truck makers touting the advantages of their 4-wheel drive (4WD) and all-wheel-drive (AWD) vehicles. But what exactly differentiates these systems from each other, or from 2-wheel-drive (2WD) systems? And how do you choose which transmission type is best for you?

To help you make more informed choices, let’s take a look at the basic mechanics of each system, its pros and cons, and the types of driving environment to which each is best suited.

4-Wheel Drive
Basically, 4WD distributes power to all four wheels by means oftwo differentials and a transfer case, delivering power to the wheels that need it most. 4WD remains disengaged until switched on by the driver, allowing you to choose when it’s needed. When 4WD is disengaged, the vehicle operates as in 2WD.

Pros
One advantage of 4WD is that it boosts traction at low speeds—making it an excellent choice if you frequentlyencounterunpaved roads, mud, rocks, snow, ice, or heavy rain. And because you switch it on only when needed, it saves you moneyon fuel costs when disengaged.

Cons
Because 4WD requires some extra engineering and equipment, it adds weight to the vehicle, and because it’s something of a premium feature, it also adds to the sticker price. Also, 4WD differentials require oil changes (separate from engine oil changes), which can increase routine maintenance costs.

Is it right for you?
If your routine travels take you no further than the office, school, or the mall, you may not want to go the added expense of a 4WD vehicle. But if you routinely drive in harsh road or weather conditions, or haul heavy loads, the added stability and control can be life-savers.

All-Wheel Drive
Unlike 4WD, which can be switched on or off by the driver, most AWD systems are always engaged. Mechanical AWD uses front, central, and rear differentials to distribute power, whereas electrical AWD uses sensors mounted on each wheel, and an engine control unit that uses this information to send power to the wheels as needed.

Pros
AWD offers better acceleration than a 2WD vehicle and provides more control and grip on slick surfaces, as well as improved traction in all weather conditions.

Cons
Because AWD systems are heavy and complex, they add both weight and price to a vehicle. And because AWD is always engaged, it tends to lower the fuel efficiency of the vehicle. In addition, differentials require oil changes (separate from engine oil changes), which can increase routine maintenance costs.

Is it right for you?
If you’ve in an area where snow, ice, freezing rain, or muddy, pitted roads are common, AWD can give you the peace of mind in knowing your vehicle s sure-footed in any and all conditions.

Two-Wheel Drive
These days most 2WD vehicles (coupes, sedans, minivans) are front-wheel drive (FWD). FWD is more space efficient, offers better traction when climbing, and delivers better control (less fishtailing) because the engine is essentially “pulling” the car, rather than “pushing” it. You’ll still see rear-wheel drive (RWD) on older (classic) vehicles and on high-performance cars because it better balances the vehicle’s overall weight front-to-rear. RWD is also used commonly on heavy-duty trucks that prioritize hauling power over speed.

Is it right for you?
If your daily driving is confined to well-maintained roads and you live in a place where harsh weather conditions are a rarity, today’s 2WD provide ample safety and control features. But f you need to haul a heavy load or negotiate an unpaved mountain pass, you may want to ask a friend with a 4WD or AWD vehicle fore a ride.

We hope this quick fact sheet helps you understand the basic mechanics of these transmission types and helps you make more informed choices at the dealership.