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, the entry-level 191bhp 220d really is all you need. There’s plenty of power low in the rev-range, so you don’t have to work it very hard at all to make brisk progress, and flat-out acceleration is pleasingly brisk. Indeed, it’s a fair bit quicker than an Audi Q5 40 TDI and destroys the Land Rover Discovery Sport D180. If that’s not enough, though, there’s a 242bhp 300d that’s noticeably more muscular, but the six-cylinder BMW X3 30d feels even stronger.
But what if you’re trying to ditch diesel? The GLC 300’s petrol engine develops 254bhp and matches the 300d for acceleration from 0-62mph on paper. However, there’s a more noticeable performance gap on the road; the petrol engine 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 with 503bhp – enough to make it the fastest sports SUV we’ve yet tested. Both models are covered in our separate Mercedes-AMG GLC 63 review.
Suspension and ride comfort
Mercedes offers three different suspension systems for the GLC. Opt for entry-level Sport trim and you get so called ‘comfort’ suspension which, when combined with small wheels, does a reasonable job of living up to its name. However, potholes and other road scabs can send a bit of a thump through the car’s structure, so it’s less comfortable than a Land Rover Discovery Sport. Move up to AMG Line trim and you get ‘sports’ suspension, but we’re yet to sample this.
Top AMG Line Premium Plus Ultimate models get air suspension as standard. Although this can be softened to give a pleasing waft at speed, the model’s 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 level with smaller wheels, either. If comfort is everything, we’d recommend looking at an air-sprung Audi Q5 instead.
The Mercedes GLC handles well enough for a large SUV. Even on regular comfort suspension, the GLC stays relatively upright through corners and grips the road well. Go beyond this limit and the stability control is very sharp in its intervention.
Air sprung models give you the option to stiffen the suspension for better cornering, but the BMW X3 and Audi Q5 both prove sharper in the bends.
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 than was previously the case. Even so, it can’t quite match the Q5 40 TDI for hushed refinement.
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 GLC 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 with the 300 petrol engine.
Just bear in mind there's a fair bit of road noise if you choose big wheels, making motorway journeys less peaceful than they might be.