BMW 320d v Audi A4 2.0TDI v Merc C250 CDI

The Merc immediately impresses with its build quality. The doors shut with all the solidity of a bank vault and there’s a certain heft to everything. The beautifully layered door pads, the sporty steering wheel and the black-and-silver-themed cabin tell you that you’re in something special. If we were to pick faults, it would be with small details like the cheaply finished steering-mounted controls and the fact that the Merc’s COMAND driver interface is nowhere near as the ones in the 3-series and the A4. Also, apart from the three-spoke steering wheel and the dials, the rest of the dashboard looks pretty conventional, with a whole lot of buttons cluttering up the centre console.

No such qualms with the Audi – the crisp dials and large display between them are the best-looking of the lot, and the MMI system also has the nicest interface of the three. Fit and finish are exceptional and the beige theme and four-spoke steering wheel point to the Audi’s relaxed nature. In fact, it is the Audi’s cabin that feels the brightest and broadest here.

The 3-series’ cabin is unmistakably BMW and is the best-looking of the three. Impressive bits include the thick-rimmed steering wheel, the 5-series-like dashboard layout and the large display for all the iDrive functions. The front seats are by far the most comfortable of the lot. Unlike the flatter and harder buckets in the A4 and C-class, the new 3-series’ seats offer far better cushioning and all-round support. The driving position is the best too and, like all BMWs, the centre console is tilted towards the driver.

However, cabin quality isn’t much of a step up from the outgoing 3-series and, like before, the buttons on the dashboard are too small and fiddly to use. But to make up, the iDrive controller, with its sub-menus and brilliant graphics, is extremely user-friendly.

At the rear, the 3-series wins again. It has the best legroom and the seats are the most supportive and comfortable. The A4 has decent legroom too, but loses out because it is a bit short on thigh support, whilst the C-class’ rear seat feels the most cramped. Also, the seat base is noticeably shorter in the Merc than in the others and the all-black theme doesn’t give you a feeling of spaciousness. All three cars are best as four-seaters; the high transmission tunnels and rear air-con vents discourage carrying an extra passenger.

All three have usefully big boots, but it’s under the boot floor that the big differences lie. The 3-series obstinately sticks with run-flat tyres, so there’s no spare. The A4 gives you the safer option with a space-saver, and the C-class is the safest bet with a full-size spare. 

All three cars come with eight airbags each, apart from a whole gamut of features to keep you safe in the event of a collision. And just as you’d expect, all of them also come loaded to the brim with features. Apart from xenon headlamps, powered seats and automatic climate control, they all get Bluetooth mobile connectivity for their audio systems. But while the BMW and Audi feature reversing cameras, the Merc relies on sensors to guide you while parking. That said, the C 250 CDI is also the only car here to feature electric adjustment for the steering and twin sunroofs that allow lots of light to enter the cabin. However, the Bimmer, in Luxury trim, wins itself a few brownie points by offering a fully functional satellite navigation system. 

The business end

Sheer bragging rights belong to the C 250 CDI with its 2.2-litre twin-turbo diesel engine. It is the biggest engine here and makes 204bhp and a healthy 51kgm shot of torque. But the C 250 CDI is slower to 100kph than the 320d because it weighs more and the BMW makes full use of its closer-stacked gear ratios. It’s only near 150kph that the Merc catches up with the 320d, and then its extra lungs kick in to get to 200kph a whole two seconds before the BMW. The C 250 CDI’s power and torque, combined with the relaxed seven-speed auto, make it especially effortless, and this is even more true in the higher gears, where its sustained thrust is something to revel in. But there are a few hiccups, the first being the gearbox’s reluctance to follow commands fed in via the paddle-shifters. Most of the time, the gearbox is reluctant to respond, the electronics choosing to follow throttle inputs and engine revs rather than frantic tugs at the paddles. Press a small button marked ‘M’ (for manual mode) and it gets better, but is still nowhere near as responsive as the 320d’s eight-speed auto.

The 320d’s gearbox response feels as quick as a twin-clutch unit, without the associated jerkiness, and that makes it one of the best automatics around. There’s a tiny delay when you mash the throttle, but once the power kicks in, the upshifts are smooth and seamless.

Though it beats the C 250 CDI in the dash to 100kph by a scant 0.14 seconds, in the real world, the 320d’s responsive nature makes it feel much quicker. It’s clearly the best performer, and when you consider that BMW’s 1995cc diesel motor is 23bhp down on power, it makes it even more impressive.

The A4 2.0 TDI is completely outclassed by the other two – it makes a mere 141bhp and 32.63kgm of torque. In reality, however, that’s more than adequate. The A4 is equipped with an eight-step Continuously Variable Transmission (CVT), and as boring as that might sound, it isn’t. The gearbox has been programmed to behave like a regular automatic and the way it shifts gears will convince you there’s a set of gears deep inside its guts. It’s only when you ask for a kickdown in ‘normal’ mode that it displays that ‘rubber-band’ effect that you usually get from CVTs.

As expected, it is nowhere near as fast as the other two in a straight line – the engine runs out of steam a lot earlier than they do – but for everyday driving, it has enough grunt for this to not be a huge issue. It is responsive, willing to downshift to make the most out of its limited power, and very linear in its power delivery.

You can see the A4’s unstressed nature in the way the engine is the quietest and smoothest. Its vocal range never exceeds ‘muted purr’ and it’s smooth enough to trick you into believing it’s running on petrol. The 320d’s engine, on the other hand, is gruff and quite audible when it’s happily revving to its 5000rpm redline, but settles down to a murmur when you’re cruising. It’s the C-class’ engine that literally makes the most noise about how much power it’s pumping out. It sounds very gruff when accelerating and, even when you’re cruising, you can hear a distant drone from under the hood.

Both the 320d and the C 250 CDI come with overt fuel-saving tech like stop-start systems, and the BMW goes one up by having an ‘Eco Pro’ driving mode that even controls the working of the climate control. The A4 relies more on stuff like reduced internal friction for the engine and the CVT to squeeze the most out of every litre.

When it’s time to brim the tanks, the 320d claims another crucial victory. It was the most fuel efficient in the city (we ran it in Eco Pro mode), returning 11.1kpl. On the highway, the BMW proved the most frugal again, sipping a litre for every 15.5km. The A4 2.0 TDI was not too far behind, returning 10.9kpl and 15kpl respectively while the C 250 CDI was the least efficient, drinking 10.1 and 14.3kpl for the same city and highway cycles.

At low speeds, it’s the A4 that feels best over bumps and bad roads. You could even describe the ride as pillowy, and this goes well with the laid-back nature of the car. However, up the speed a bit and the A4 is less composed. The body wallows and pitches excessively and never settles down to the flat ride you expect from a German car.

The 320d doesn’t have adjustable dampers like the European-spec version, but despite this omission, the overall ride quality is simply outstanding. The suspension is tuned to be on the softer side and hence, at city speeds, the BMW is almost as pliant as the A4 and equally comfortable. At higher speeds, there is some vertical movement, but the overall body control is far better than the A4’s. As a result, the 320d feels much better planted than the Audi and inspires far more confidence too.

What’s annoying with both these cars, though, is the way the suspension rattles over sharper bumps.

The C-class, by contrast, is stiffer at low speeds with sharp, vertical movements over uneven surfaces, but go faster and the ride becomes supremely flat. Switch the adjustable dampers (exclusive to the AMG edition) into Sport and there’s a noticeable difference in the way it handles. On the harder setting, the C 250 CDI is unshakeable at any speed and has fantastic poise. The steering doesn’t feel particularly precise, but it’s got a wonderfully fluid feel to it that you only get with a traditional, hydraulically powered system.

However, it’s the 320d that provides the most thrills, and this is mainly down to the brilliant chassis balance and relatively quick steering. The BMW feels more agile than the other two and is more eager to change direction. It rolls a bit more than the C-class and mid-corner bumps can unsettle it a bit, but that’s a trade-off you get with softer suspension.

The A4 is the least sporting of the three – it doesn’t have trick dampers and its front-wheel-drive architecture doesn’t encourage spirited driving either. There’s decent grip, but lower power and the fact that it rolls and pitches too much make it more suited to a relaxed driving style.

Around town, it’s the A4 that’s the easiest to drive thanks to good visibility and its light steering. The BMW and the Merc cabins make you feel more cocooned but, on the flip-side, their thick, raked pillars limit visibility.

Crunch time

In the end, the A4 makes a good case for itself as the office commuter. It’s a great car to drive around town, thanks to its soft ride and light steering. The smooth and silent engine adds to its user-friendly demeanour. The rear seats are spacious, the cabin is airy and the understated looks are still classy. But ask more of it and the A4 will fall short. Smaller, cheaper saloons can embarrass it off the lights, it isn’t as capable as the others at higher speeds and it isn’t particularly exciting to drive either.

The C 250 CDI tries to win you over with its sheer grunt, unflappable poise and solid build, but again, the engine is the least refined, it isn’t as spacious as its rivals and, frankly, the C-class is now getting a bit long in the tooth.

The new 3-series, in comparison, is an outstanding all-rounder. The generous seats and absorbent ride make it the most comfortable to sit behind the chauffeur in. When you want to play, the brilliant performance and entertaining handling are a cut above the others too. Sure, the engine may not be the quietest around and interior quality isn’t a big step up, but these things are easily overlooked when you see how complete and well-rounded the rest of the car is. Factor in the stunning looks and best-in-class fuel economy, all of which are yours for a price tag that is not over the top, and the 320d’s value proposition only gets stronger.

It’s an easy victory for BMW, which has gone on to set a new benchmark in this class.