2WD versus AWD SUV: Which is best? | Auto Expert John Cadogan

2WD versus AWD is the classic SUV dichotomy - and the default presumption is: AWD is better. But the truth is, a lot of this depends upon you and how you’ll actually be using the vehicle.
Mary’s question about this is pretty typical:
“I’m looking for a good SUV. I’ve been told AWD is a better safety choice as there is more control in braking. I am doing a lot of driving between Ulladulla and Sydney and often have the grandchildren with me, so this is obviously a concern. Can you help?”
Some simple advice up front: If you want to go off-road adventuring exploring, on fire trails, whatever: get the AWD.
You do not want to be in a position where you drive down some fire trail to an idyllic campsite, where you can burn the dinner and commune with nature, listen to the kids bitch about not having WiFi all night and then it rains in the morning and you can’t get home because … 2WD + muddy ascent equals fail.
Regular trips to the snow, launching a boat on a ramp, rural property with driveway from Hell - all excellent reasons to own the AWD.
But if you want an SUV really only to act in the capacity of a defacto family station wagon - and that’s all you want it to do - you probably don’t need AWD. In fact, if you’ve had a car all these years, and you’re getting an SUV, and you don’t plan on driving any differently, 2WD will be fine.
The first thing to remember is that plenty of SUVs are only 2WD. Nissan’s Qashqai and Honda’s HR-V, for example, are 2WD only. And the base models of plenty of other SUVs - like the Mazda CX-5, Kia Sportage and Hyundai Tucson - the base models are all front drivers.
At this point, let’s put Subaru in a box on its own - that company only does AWD. And it’s a unique-ish selling proposition. In fact, Subaru’s Symmetrical AWD is an excellent system and (together with their involvement in rally) it rocketed them from obscurity in the 1990s to where they are today in the mainstream.
In Subaru’s case - all-wheel-drive really does mean all the wheels are driving, all the time. But in the majority of the rest of the market … not so much. We’ll get to that now.
Most AWD systems are ‘on-demand’: meaning they are predominately, overwhelmingly, 2WD for the vast majority of their operational lives. AWD is only invoked when there is front wheel spin. When the front wheels lose it, that’s the demand for all-wheel drive.
So let’s be perfectly clear - your common, and notionally AWD SUV, just driving down the street normally, is doing so under the tractive effort of just the front wheels. It they’re not threatening to spin, the rear wheels aren’t threatening to drive.
Sure - you can lock AWD in, manually. Locking in AWD is a really good idea in that ‘rain overnight/camping’ scenario we discussed earlier.
But it’s a really bad idea at other times - especially on high-traction surfaces, where driving in AWD will start scrubbing out the tyres and (potentially) break the transmission. Good safety tip there. Leave it in auto.
You have to remember that the front end of the car and the rear end follow slightly different paths when you drive around curves. Therefore they travel different distances. Therefore they need to turn at different rates. If you lock them together by pressing the button, and traction levels are high, there’s an excellent chance you’ll break something.
Subaru gets around this problem with a viscous coupling just behind the gearbox. It’s a bunch of precise hardware swimming in very thick silicone fluid, and the upshot is that it allows the front and rear prop shafts to turn at different rates without blowing up.
Apart from additional traction in slippery conditions - the purported advantages of all-wheel-drive for ordinary drivers pretty much just fluff.
AWD used to be a huge contributor to overall dynamic stability. But then, when the dinosaurs all died and Twitter was invented, cars came with a bunch of other stability-enhancing systems (like electronic stability control) that have levelled the playing field by making 2WD vehicles just as stable in most driving scenarios.
People say AWD gives you more grip, but this is unmitigated bullshit. Grip is a function of rubber on the road - it’s not a function of which wheels are driving. What AWD does, however, is reduce the tractive effort at each wheel for any given throttle input.
In other words - AWD makes it more likely you’ll be able to maintain traction in slippery conditions where equivalent 2WD system would be spinning their tits off like a pole dancer on crack.