BMW 6-Series GC takes on the rivals

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Do any of the bosses of the top-end German car companies actually possess a passport? To judge by their cars, they spend all day, every day twitching their curtains to see what their neighbours are up to, rather than lifting their eyes to the global horizon. The limit-free autobahn sections would net you about a one-and-a-half hour time to get from Stuttgart to Munich. Munich to Ingolstadt is a lot less. And in this little southern German neighbourhood, BMW and Audi and Mercedes have a comically obsessive habit of keeping up with the Müllers. They match each other on specs, on technologies, on suppliers. If any one of the three builds a new niche car, the rest follow. Mercedes made the CLS, and inevitably BMW and Audi followed.

Words: Paul Horrell
Photos: Matt Howell

This feature first appeared in the July 2012 issue of Top Gear magazine

And you know what? This apparent insularity is why they do so well globally. The heat of this local competition keeps each of them honest. None of them could afford to slacken off and build a bad car, because it would be so obvious in the light of their rivals' excellence, and the large, wealthy local German market would turn up its nose. (Conversely, for decades, all the Detroit Big Three got away with building shoddy cars because their neighbours built shoddy cars too, so the local market kept loyally buying the crap.) In southern Germany, excellence is expected and excellence goes down well among prosperous drivers across the world.

Sure enough then, none of these is a dud. And we suspect that most people choosing between them will take their pick mostly on the simple basis of which one they like the look of. Prefer simple, minimalist lines? The A7's your car. Want a full-fat dose of visual complexity, billowing folded metal wearing blingy lighting clusters ? Head for a CLS. The box-fresh BMW 6-Series Gran Coupe prudently sweeps up the middle ground, as it's more flamboyant than the Audi and less baroque than the Benz. But it actually has more dramatic proportions than the others. That's because while the A7 and CLS are based on saloons, the A6 and E-Class, the Gran Coupe is a stretched coupe. So it looks the lowest and swoopiest car of our group.

But even though they might be style-driven, we can't just judge them on looks alone. We're here to drive, and it turns out that for all the benchmarking that goes on, the 6-Series Gran Coupe doesn't feel exactly the same as the Audi A7, and that, in turn, is different from the CLS. Some of the differences are subtle, some dramatic enough to have surprised us.

The CLS350 CDI is a bit of a TG favourite, having beaten an A7 in a previous test and been super-popular in our long-term test garage. So why is an A7 back here? Because this one has the new BiTDI engine. And the new kid is the 640d Gran Coupe.

Forget the numbers on the bootlids. They don't correspond to engine sizes. The Audi is a 2.7, the others 3.0 litres, and all have six cylinders - V6 for Audi and Mercedes and straight-six for BMW. The Audi and BMW have the same eight-speed ZF auto 'box (replacing the seven-speed twin-clutch in lower-powered A7s), and Mercedes uses its own seven-speed auto. It's rear-drive for the Mercedes and BMW, quattro for the Audi. The Audi and BMW both use sequential twin turbos - a little one to get things moving at low revs, and a big one for more puff higher up. That gets them each to 313bhp, rudely healthy power for diesel engines.

And the thing is, the new Audi engine doesn't sound like a diesel either. Honestly, as it careers between 3,500rpm and beyond the big five (that's major revs for a diesel) it reminds me of the noise of the classic Alfa V6 petrol. Actually, Audi cheated - there's a loudspeaker in the exhaust that adds to the effect, but, when you hear it, you probably won't care it's cheating. The BMW sounds more dieselly, but it's still a straight-six so we aren't complaining. These two - as you'd expect given they have the same power, very nearly the same torque and weight, and the same auto 'box - are, for performance, to all intents and purposes, matched. They're plenty quick.

But if it's slippery, the Audi scoots out of tight wet corners and roundabouts while the BMW is still flashing its traction light. Real-world, then, it's the fastest car here. But sometimes it feels quite the opposite. BMW's eight-speed 'box is telepathically good at matching its ratio to the engine's torque and the way you want to drive. The Audi's 'box sometimes leaves you becalmed in too high a gear, and hesitates before kicking down a couple of ratios, hitting engine boost and catapulting you away as absurdly rapidly as it was, a second ago, frustratingly languid.

The Mercedes makes very similar torque to the other two, which means in the low to mid revs it matches their performance. But then it runs out of puff while they'll keep steaming to higher revs and higher power, so if you wring the engines right out, the Mercedes is left behind. Its 0-62 time of 6.2 seconds is far from lazy, but the others are in the low-to-mid fives. That said, except during banzai overtaking, the Mercedes hides its deficit well.

Sometimes though, you wonder if the Mercedes has an engine at all. Not because it can't haul itself along, but because it's so quiet. Amazingly quiet for a diesel. At open-road speeds, especially if there's some other commotion like a coarse road surface or swishing 'screen wipers, you barely hear the engine note change as it shifts up the gears. Which makes it slightly uninvolving for a back-road blat. But the rest of the time the Mercedes powertrain is a marvel. Gear shifts aren't just inaudible, they're indiscernible because everything happens so smoothly. And the engine is the quietest at urban speeds too.

We ran the three cars in convoy, sharing the driving in all the different types of conditions of a drive across England, to and around the best roads in Wales. Fuel consumption was close enough not to matter, with the Audi at 29.4mpg, and the BMW and the Benz both, within the limits of experimental error, at 30.5. The unrepresentatively gentle official tests give them all numbers in the mid to late-40s, again an insignificant difference unless it matters that the BMW's sub-150g/km number slips you into a tax bracket.

The next bit, discussing handling and ride, comes with the proviso that we're talking about the cars as they ponied up on the day. Both the Audi and the Mercedes can be optioned with adaptive air suspensions. But they weren't. The Mercedes' 19-inch AMG wheels are included in the Sport model. The Audi has the lowered and slightly stiffer springs that come with the S Line kit. S Line normally means 19s, but this one has 20s. The test BMW is rocking quite an outfit: its M Sport spec brings 19s, but it's wearing 20s here, plus a £3,400 package of switchable adaptive dampers and active anti-roll bars. No active steering on this particular one though, and we're not missing it.

The BMW is the most amusing handler. You can lean on it through corners and feel each tyre work, and balance their loads with the accelerator. The steering's weight is a little gluey, but the feel comes through. The Mercedes isn't quite as tightly damped, and there's a bit less steering feel and a bit less accelerator-sensitivity, but it runs the BMW close.

The Audi meanwhile just grips and grips. It feels neutral and balanced, but a bit dead-eyed. Still, if it's wet, the immense traction really is useful. As a side note, the handling on our TG Garage A6 Avant quattro (same chassis basically) felt much more interesting and "delicate" according to its regular driver when it switched from 20s to 17s with winter tyres.

That change also helped the ride. Help the A7 could very much do with. It clumps and thumps, and, worst of all in a big long-distance cruiser, kicks up a grinding squall of tyre noise on many A-road and motorway surfaces. The BMW does a usefully better job of rounding off most bumps, especially with the chassis in its Comfort setting (I drove like that, instead of Sport, on lumpy twisty roads too, as it makes the car feel more fluent). But, like the Audi, if to a lesser extent, there's a sharpness and noisiness underlying it. Also, the BMW can jostle side to side on a rural road. This doesn't affect your speed, but it's noticeable after the CLS. It's also more susceptible to motorway crosswinds than the CLS.

Oh, wow, the CLS. Its standard equipment includes a road crew resurfacing everything just before you get there. They don't always do a perfect job, these guys in hi-vis and hard hats, but they've sure improved it since you went there 10 minutes ago in your BMW or Audi. And despite this softness - on big bumps and small - there's no lack of damping control. It's a superb natural non-adaptive set-up. The sort of thing we thought only Jaguar did.

This lovely quiet ride, and the murmuring engine, are terrific assets away from the tear-arse environment of a road test in the Welsh hills. In town, what more could you want than the CLS's near-silent glide? And if you had to drive overnight tonight to - where d'you fancy or need to be? Bordeaux? Milan? Prague? Berlin? - well, the CLS is, beyond doubt, your car. If it were rubbish weather though, or Zermatt, then, by all means, the Audi. But do change its tyres first.

All the interiors are great places to spend long hours. The Mercedes' seats support most snug in corners, and the same applies in the back, but that's because they're two-person buckets and the others have benches. The CLS driver's cushion is hard and flat. Some like it that way. I preferred the Audi and BMW seats on the motorway haul.

The style of the cabins matches the exteriors: the CLS rather ornate and touchingly individual, the Audi austere, the BMW just right. All are beautifully crafted. There's no longer much to choose between the navigation, snappiness and graphics of BMW iDrive, Audi MMI and Mercedes COMAND. They all bundle in, as standard, nav and phone Bluetooth. Those functions and the hi-fi are upgradable on all the cars, but they're perfectly decent as is.

Mercedes, despite its reputation for po-faced functionalism in ergonomics, has made some mistakes. The silver switches and silver dials have bluish silver backlit markings so are unreadable unless it's very bright or very dark outside. And the matrix screen in the middle of the CLS speedo is pathetically small against the wonderfully big and well-used one between the Audi's speedo and tach.

If you need five seats, the CLS rules itself out. Want a hatch for bulky loads? Get the Audi. But the others provide folding seats too. For rear space, the Mercedes' two occupants do best. The Audi is good for legroom, but the heads of the tall will brush the ceiling. The BMW is shortest of rear foot space.

The Mercedes came with almost no options and it's fine. The £53,500 for Sport trim looks like the bargain of the group. The Audi's list for S Line trim (which we're not entirely sure we like) is £55,040, and that includes more power than the Mercedes and two more driven wheels. The test £63,350 A7 added optional posher MMI, a head-up display, Bose sound, adaptive cruise, lane keeping and side blind-spot warning. The BMW is expensive. In M Sport trim it's £68,565 (even the SE, different only in cosmetics really, is still £10k more than the CLS). The test car had an optional HUD, fancy adaptive chassis, 20s and more, none of which it needed, but they put it £30k above the test Mercedes.

The Audi A7 to buy isn't the A7 that's here. We'd forget the S Line and get the SE, for its softer springs and 18s, and that'd go some way to solving the harsh ride and the road noise. We love its engine and traction. The hatchback makes it useful, but the roads are full of five-door hatchbacks, so it seems less special than the CLS and 6-Series.

The Mercedes is the cheapest car here, but the one that moves most expensively. It's the quietest, the smoothest,the best-riding and the best in town or the suburbs or on motorways, which are the environments these cars will almost inevitably spend most of their time in. As it happens, I don't like its looks, but you might, and if you did, it's a finely engineered choice.

Probably not the one we'd take home though. We'd have the BMW. Sure, it's not as civilised as the Mercedes, but if you steer clear of the hard damper settings, it doesn't do a bad job of impersonating the to-the-bone luxury of the Mercedes. And, on an interesting road, the BMW is the most captivating, because, compared with the Mercedes, you feel more of what its chassis is up to, and hear more of what its engine is up to. Looks matter, and it's our favourite, but driving matters more.