Push hard and you'll know about it, with a pronounced diesel grumble towards 3000rpm and some vibration through the wheel and pedals. At motorway speeds, the standard 18in wheels kick up a fair bit of tyre roar and there is noticeable wind noise around the A-pillars and front side windows, although the engine has settled down by this point.
Where the Q30 trumps the A-Class is on ride quality, with Infiniti's engineers apparently investigating more than 50 damper settings and spending time making sure lighter and heavier engines in the range get bespoke settings to achieve a decent level of comfort across the range.
Sure, the largest, sharpest potholes still cause some shudder through the body, but for the most part the Q30's dampers and standard large-profile tyres manage to get it across broken surfaces and expansion joints without unsettling those onboard. The only grievance is the amount of thumping heard in the cabin as it does so.
The Q30 can't claim to mix with the dynamic leaders of the class, either. There's decent grip, with up to 50% of the power available to the rear axle should the front wheels wash wide or lose traction, and Infiniti has crafted an evenly weighted (if rather heavy) steering system. Front-end responses never feel sharp, dulled further by those large-profile tyres, and the Q30's body tends to lean further than the class's most agile occupants in corners.
Inside, there's good space for two tall adults in the front seats and plenty of adjustment for the driver, even if the driver's seat provides too little lateral support. The rear seats are far more cramped, forcing adult knees into the backrests in front and forcing a middle passnger to contend with little shoulder or foot space. Adults will find the sides of their heads touching the protruding ceiling above the rear window, which itself tapers to quite a claustrophobic depth.
Boot space rivals the class best, though, and living with its square shape and decent access won't present many problems. It's a shame that there's no adjustable floor and that the underfloor space is limited. Overall, though, this is one of the Q30's best interior assets.
In part, interior quality deserves praise, too. The upper sections of the dash, the door cards and the dash and door trim inlays are soft to the touch and the metallic bits are suitably stout. However, the plastics further down the dash and centre console are less convincing, and being forced to embrace a lot of Mercedes' electronics and switchgear isn't good for perceived quality.
Inifiniti's own infotainment system is hard to get excited about, too. The standard 7.0in colour touchscreen can also be controlled using a rotary dial and shortcut buttons between the front seats, and DAB radio, Bluetooth and voice control feature on every model. Screen graphics are sharp, but the system lacks the responsiveness or latest connectivity apps of its best rivals, while the clunky sat-nav is a £1400 option even on our mid-range Premium Tech car.
Still, Premium Tech trim does include features such as leather seats, climate control, keyless entry, a rear-view camera, two USB ports and, like all Q30s in the range, city braking technology as standard.