Engine, 0-60mph and gearbox
The 2019 facelift introduced three new engines to the GLC, a 2.0-litre petrol and a 2.0-litre diesel that's available with two power outputs. Sticking to the black pump, we’ve so far only sampled the 242bhp 300d which proves more than strong enough. There’s plenty of power low in the rev-range so you really don’t have to work it very hard at all to make brisk progress and flat-out acceleration is impressively strong. Still, the six-cylinder BMW X3 30d feels even stronger.
But we suspect the petrol engines will be of more interest to UK buyers. The GLC 300 has 254bhp and matches the 300d for 0-62mph acceleration. However, there’s a more noticeable performance gap on the road, as the petrol needs working harder than the diesel should you feel the need for speed.
At the top of the tree sits the bonkers fast GLC 63 with its 4.0-litre twin-turbo V8. And of course, if 469bhp isn’t enough, there’s the GLC 63 S which gets 503bhp, enough to make it the fastest sports SUV we’ve yet tested.
Suspension and ride comfort
Mercedes offers two different suspension systems for the regular GLC. Most models have an adaptive system that allows you to stiffen and soften the ride to suit your mood. Unfortunately, we haven’t experienced this set-up yet.
Top AMG Line Premium Plus Ultimate models get air suspension as standard. Although it can be softened to give a pleasing waft at speed, standard 20in wheels pick up on surface imperfections so the GLC never quite seems to settle down. Annoyingly, you can’t choose air suspension on a trim with smaller wheels, either. If comfort is everything, we’d recommend looking at an air-sprung Audi Q5 instead. If you’re curious about the AMG GLC 63, then take a look at our separate four-point review for more information.
The Mercedes GLC handles well enough for a large SUV. Once again, we’ve only tried the air suspension, which allows you to stiffen things up to reduce body roll, and the GLC stays relatively upright through corners and grips the road well. However, it doesn’t feel quite as sharp as the Q5 or BMW X3.
It’s a real pity the GLC’s steering isn’t better; it weights up in a rather unnatural way when you turn in to corners and, because the steering is variable (it gets progressively quicker as you apply lock), it's hard to corner precisely at faster speeds.
Noise and vibration
Although the pre-facelift GLC suffered from gruff diesel engines, the latest 2.0-litre unit is much improved. It sounds much less clattery and sends fewer vibrations through the steering wheel. We suspect it has the measure of the X3 20d, but the Q5 40 TDI still has the most refined four-cylinder diesel in the class,
The petrol 300 is pleasantly hushed, particularly at low speeds where it’s quieter and smoother than the four-cylinder diesel alternatives. Indeed, it actually sounds like a six-cylinder, thanks to some heavy noise augmentation using the stereo’s speakers. Don’t worry, though – unlike some such engine noise generators, this one is fairly convincing. AMG 63 models on the other hand sound like Ares the God of War gargling with heavy artillery.
The standard nine-speed automatic gearbox shifts smoothly most of the time, even if it’s a little hesitant when accelerating from a standstill. The start stop system works smoothly, especially in the 300 petrol.
Just bear in mind there's a fair bit of road noise if you choose big wheels, which makes motorway journeys less peaceful than they might be.