The 2015 RDX starts with a great engine tucked into a solid chassis. Under the hood, the new 3.5-liter V-6 outputs a maximum of 273 horsepower and 251 pound-feet of torque. You won't always need all of that power all of the time, so the RDX's V-6 has a neat trick that helps it to save fuel.
A V-6 that's sometimes not
In low-demand situations, such as when cruising at low speeds in the city or coasting along on the highway, the V-6's Variable Cylinder Management (VCM) system can reduced the engine's displacement by shutting down a few of its cylinders. When you're poking through the toll plaza line or creeping through a parking lot, the RDX can drop down to an inline three-cylinder by shutting down one of its banks. When you're coasting along at the speed limit on the highway, it can shut down two cylinders at opposing corners of the V's two banks to run as a V-4. And when you need the power for accelerating or climbing, it can seamlessly fire up all six pots for the maximum output. What's most notable is how smoothly and constantly it switches between these three modes depending on the needs of the engine. If no one told you about it, you'd probably never know that your RDX's engine was a transformer.
At the business end of the V-6's crankshaft is a six-speed automatic transmission that features sport and manual shifting modes, the latter augmented by standard paddle shifters. This one is not at all a bad automatic. In its sport mode, it fires off quick gear changes and even holds the current gear when braking for a turn (rather than upshifting in mid-apex) to help keep the SUV settled. In its standard mode the shifts are still quick, but become smoother and less obtrusive.
Intelligent Control all-wheel drive
The 2015 RDX is available with all-wheel drive, but not the Super Handling all-wheel drive system that we've seen in the Acura TL and MDX models and previous generations of the RDX. This is a new on-demand system, basically a 100-percent front-wheel drive setup under cruising conditions that can send up to 25 percent of available torque to the rear axle during dry acceleration and cornering.
However, when the road gets wet and slick, something theoretically odd happens. In really slippery conditions, the Intelligent Control AWD system reduces engine output to the front wheels to bring the system to a nearly 50/50 torque split, albeit at a lower total output. It's less sophisticated than the SH-AWD system; there's no rear-axle torque vectoring or on-demand rear power bias when cornering like you'll see on the more impressive system.
In this case, AWD is a safety feature rather than a performance upgrade, and should be viewed as such. Plus, the sort of low-traction situations where the RDX would need to rein in its power are probably not the sort of situations where the average driver would need a lot of torque.
Regardless of how you choose to view the RDX's new all-wheel drive setup, we can probably agree that the on-demand nature of this lighter system doesn't make too big a dent in the SUV's decent economy. The EPA reckons the 2015 Acura RDX AWD will do 19 mpg in the city, 27 mpg on the highway, and 22 mpg combined; that's just 1 mpg down across the board from the front-driver's estimates of 20 city, 28 highway, and 23 combined miles per gallon. I got 21.6 mpg during my mixed cycle testing over the long Independence Day weekend.
Acura leaves a few mpgs on the table by not opting to equip the V-6 with direct injection or by using stop-start or anti-idling technologies.
A few mixed messages
The RDX's chassis feels well sorted and didn't creak or rattle over bumps, but its suspension is quite stiff, especially over small potholes and cracked asphalt. So while the RDX's frame was unflappable, the passengers within were jostled and bounced quite a bit. This over-firmness can make the RDX a bit unplanted when cornering over rough roads. Both On Cars' Brian Cooley and I noticed that the RDX seemed to skip over bumps while cornering rather than soaking them up.
At the other end of the sport-comfort spectrum is the RDX's steering wheel, which is totally devoid of road feel through its electric power-assist system. I'd expect a car that's sprung so tautly (and a Honda at that) to have a weightier steerer and a more direct feeling, but the RDX sometimes gave me the impression that it wasn't sure if it wanted to be a carver or a cruiser.
Though the RDX uses a drive-by-wire throttle and electric power steering, the excellent driver-aid technologies present on the MDX are simply not offered here. There's no lane-keeping warning or prevention, no adaptive cruise control or precollision braking. You can't even get blind-spot monitoring or parking-distance sensors. You do get a standard rear camera, which is nice, but for a brand that typically impressed us with its advanced safety features, the RDX feels a bit spartan.