
Four-wheel drive versus all-wheel drive - What is the difference?
The terms "Four-wheel drive" and "all-wheel drive" come up a good deal in the SUV space. Though they may seem interchangeable, these are technically two different systems. And with 45% of vehicles sold in the US offering one of these two systems, it is important to understand those differences.
Both systems exist for a similar purpose, that of increasing traction in slippery conditions. They both work by distributing power among the different wheels via techniques such as differentials and couplings. And they both come in two variants, full- and part-time.
The most important distinction is that four-wheel drive is built to distribute torque among the wheels for maximum pulling power. Thus, this system is best when trying to clear a deep mud puddle or snowdrift. Off-road enthusiasts prefer part-time four-wheel drive, as they can choose to turn it on and off as conditions permit.
All-wheel drive, by contrast, distributes torque to maximize traction. As both variants of this system work automatically, it is best when road conditions are inconsistent. In these situations, it is helpful to have a system which can sense road conditions and react in less time than it would take for the driver to respond. All-wheel drive is most effective in a rainstorm or snowfall, when different parts of the road are more or less slippery.
While these systems are standard on some SUVs, most offer them as an option on certain trim levels. The systems do increase the car's weight and slightly decrease fuel economy. Also, in normal conditions, four-wheel drive offers a slightly rougher ride than all-wheel drive.
The Third-row Question
Another factor to keep in mind with used SUVs is that most models are configured to offer five seats in two rows. Some have a third row available, either as standard or as an option on certain trim levels. Before buying a used SUV, it is a good idea to decide if you require a car with a third row, which can be useful for transporting teammates, friends or extended family members.
A note on fuel economy
Generally, vehicles built later have better fuel economy than their earlier model-year brethren, due to advances in technology. While many drivers prefer efficient vehicles because they require fewer trips to the pump and are more environmentally friendly, those looking for sheer power and off-road performance may find that a less efficient vehicle offers stronger capabilities.