Mercedes-AMG CLA 45 saloon

In recent years, Mercedes, Audi and BMW have battled it out to have the most powerful models in their respective classes, and in this case Mercedes is the current winner with the 2.0-litre engine fitted in the Mercedes-AMG A 45 S and CLA 45 S. It’s the most powerful four-cylinder engine ever sold in a showroom, kicking out an astonishing 415bhp. In a world that’s turning to hybrid and electric vehicles, the Mercedes-AMG CLA 45 S feels like an act of defiance.

The CLA range is now in its second generation and is a sleeker, style-led alternative to the Mercedes A-Class hatchback and, now, the A-Class saloon. With AMG-Line being the entry point, there’s no CLA that doesn’t look sporty, but this range-topping AMG variant stands out with its even more chiselled styling. Everything’s bigger than the standard car - the grille, air intakes, bonnet bulges and exhausts (all four of them) - for a more aggressive appearance. There are even 'dive plane' flaps attached to the front bumper to help keep the nose pinned to the tarmac.

It certainly deserves its angry looks, given the power on offer. With almost no turbo lag, the CLA 45 S sprints from 0-62mph in just four seconds, and tops out at a limited 168mph. It’s faster than most versions of the Porsche 718 Cayman, and almost as fast in a straight line as the much more expensive Porsche 911.

The considerable power on offer is controlled by an eight-speed dual-clutch automatic gearbox and Mercedes' 4MATIC all-wheel-drive as standard, although you can change gear manually with the steering wheel paddles. Compared to the standard CLA, the CLA 45 S offers a suite of mechanical upgrades including massive brakes, tuned suspension and six driving modes ranging from ‘Slippery’ and ‘Comfort’ to ‘RACE’. With power going to whichever wheel needs it most, there's usually plentiful grip on offer but a ‘drift mode’ setting makes it easier for drivers to powerslide the car on track.

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You don’t need to worry that the CLA 45 S is a stripped-out, no-frills sports car though. The interior is even more special than the standard car, thanks to coloured accents, leather and microfibre upholstery on the seats and steering wheel, AMG-specific displays on the twin screens, stainless steel pedals and AMG door kickplates. We rate the interior in the A-Class and CLA as one of the best on offer, and the extras make it even more sporty and eye-catching.

Of course, a performance car like this comes with high running costs. Mercedes claims up to 34mpg, but you’ll struggle to achieve this figure in the real world - especially if you use the engine’s full power reserve - while consumables like oil and tyres are likely to cost more and need replacing sooner than they would for a standard car. It's an expensive car too, although in the grand scheme of things it’s not much more than the AMG A 45 S hatchback. As the CLA is a sleek coupe, we think it suits its price tag better than the hottest A-Class variant.

With so much power at your disposal, the Mercedes-AMG CLA 45 S was never going to be a frugal car. Mercedes claims up to 34mpg, but in the real world, with hills, traffic and other considerations, you’ll probably not see above 25-30mpg unless you drive very carefully. Thanks to its sleeker shape, the CLA 45 S is ever so slightly more economical than the A 45 S - but not by enough to notice a huge difference at the pumps.

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After the first year’s VED tax (usually included in the price of the car), you’ll be paying the standard £150 as with most other cars. Because the car costs over £40,000, you’ll need to pay an extra £325 the first five times you renew the tax, taking the cost to £475 until the car is six years old.

Your annual car insurance premiums are likely to sting because the CLA 45 S sits in insurance group 44 out of 50. Those lucky enough to consider it as a company car will pay the top rate of Benefit-in-Kind (BiK) tax, while items like tyres, brakes and the servicing will add further expense.

Many things make the Mercedes-AMG CLA 45 S feel special, but the engine is undoubtedly the star of the show. Its size is not unique - 2.0-litre, four-cylinder petrol engines are used in many cars - but the amount of power it produces is. AMG’s engineers have managed to extract 415bhp, which makes it the most potent factory engine of its capacity and type ever produced.

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The CLA 45 S is a tenth of a second slower from zero to 62mph than the A 45 S, still cracking the sprint in four seconds dead. Find somewhere long enough (and legal) to make full use of the engine’s power, and you won’t stop accelerating until you hit 167mph - and even that speed is electronically limited.

Mercedes hasn’t just upped the power and left it at that. The car has been reinforced to make the chassis stiffer and stronger. Bigger brakes also feature, and the engine has been rotated to help air intake and aerodynamic efficiency. Six driving modes are available giving drivers the choice of Slippery, Comfort, Sport, Sport+, Individual or RACE. The car is also capable of shuffling its power around to whichever wheel needs it most, depending on the road conditions. This technology also means the CLA 45 S has a 'drift' mode, so you can ‘powerslide’ around a track if you want to.

While too much performance hardware can sometimes distance the driver from the action, the latest CLA 45 S manages to both involve and entertain, improving on the old model. Accelerating out of corners, you can really feel power being sent to the rear of the car, unlike older cars that always felt like front-wheel drive in corners.

Even the standard Mercedes CLA’s interior is breathtaking, with its ultra-modern design and smattering of premium materials, but the top-of-the-range AMG CLA 45 S goes even further. As the sportiest model, it gets coloured accents on the seats, contrasting stitching and a 12 o’ clock marker on the steering wheel, plus a flat-bottomed AMG wheel trimmed in suede-like microfibre and man-made leather.

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It's fitted with Mercedes’ MBUX twin-screen setup as standard, with one side showing driving information and the other showing infotainment and navigation. This includes AMG-specific menus and features such as a real-time view of the racing circuit you’re on and guidance to show you the best racing line.

AMG’s engineers have tweaked the suspension, and the latest CLA 45 S is much more comfortable than the previous model. These changes make the car more stable at high speed helping reduce body roll in the corners as well.

Those sitting in the front will be very happy, as the seats are supportive and there’s as much space as in the A-Class. The car’s extra length means the boot space is much bigger, though; with 460 litres, it’s 90 litres bigger than the A-Class. Despite the extra performance parts, the boot size is unchanged from the standard CLA.

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However, the sloping roofline and coupe shape has its downsides. Like many saloon cars, the boot opening is far smaller than a hatchback’s - so you’ll struggle to carry bulkier items. The sloping roof also means rear headroom is far less generous than in the A-Class, so tall adults will be brushing against the roof lining and may bump their heads when getting in. With small side windows and big front seats, the rear could feel dark and claustrophobic for some, but this is improved if the panoramic glass sunroof is fitted. The Audi RS3 Saloon is better in this regard.

The Mercedes CLA and Mercedes-AMG CLA 45 S have not been tested by independent safety experts Euro NCAP yet. But both are based on the A-Class hatchback, which picked up a five-star rating, with scores of at least 90% for protecting adult occupants, children and pedestrians. Both cars share safety technology, so the CLA 45 S also gets automatic emergency braking and lane-keeping assistance as standard.

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While the CLA hasn’t been on sale long enough to comment on its reliability, the A-Class it's based on did feature in our 2020 Driver Power survey. It came a respectable 36th out of the top 75 models, with a reasonable 12.8% of owners reporting a fault within the first year. Mercedes as a brand didn’t perform as well, coming a disappointing 28th place out of 30 manufacturers (behind Audi and BMW). Just under 17% of Mercedes owners reported a fault, and common complaints included high servicing and running costs.