At 70mph in ninth gear, the crankshaft turns at just 1500rpm, and while the engine’s distant rumble persists, the GLC is refined at a cruise save for tyre roar over coarser motorway surfaces.
The car is game for B-road sorties, too. There’s a fluidity to the body control that’s genuinely enjoyable as you leverage the 250 d’s 74lb ft advantage over the 220 d between corners and its traction-bearing four-wheel-drive system through them. Sport mode makes the gearbox’s shifts more aggressive, but there’s still a delay between requesting a manual shift on the steering wheel-mounted paddles and getting it.
The steering is a more serious gripe, though. It’s overly light in Comfort mode, and while it’s responsive enough and there’s more heft to the helm in Sport, there’s a lack of weight variation, which muddies messages of grip from the front wheels. The brakes disappoint, too - they’re certainly effective but have a wooden pedal feel.
Should I buy one?
The adaptively damped GLC with air springs we drove impressed for handling and comfort, so there seems little call for the AMG Line’s firmer passive set-up. You can add air suspension to mid-range Sport specification for the same price as upgrading to AMG Line, and that seems the smarter move.
Sport is the only trim eligible for the £495 off-road pack, too, adding tools such as hill descent control, 20mm-raised suspension, underside engine guard and special traction programmes.
Official figures say there are no emissions or combined economy disadvantages to choosing the 250 d over the 220 d, meaning it beats the slightly thirstier and slower BMW X3 xDrive20d which, in M Sport trim with an auto gearbox, costs within a tenner of the GLC 250 d AMG Line. Given the Mercedes’s superior refinement and fresher interior, the X3 definitely has a battle on its hands.
Mercedes GLC 250 d 4Matic AMG Line
Location Bedfordshire; On sale Now; Price £39,595; Engine 4 cyls, 2143cc, twin-turbocharged, diesel; Power 201bhp at 3800rpm; Torque 369lb ft at 1600-1800rpm; Gearbox 9-spd automatic; Kerb weight 1845kg; Top speed 143mph; 0-62mph 7.6sec; Economy 56.5mpg (combined); CO2/tax band 129g/km, 23%