What is it?
BMW's 5-series with a new generation of four-cylinder diesel engine, offering reduced emissions and reputedly improved consumption.
Pleasingly, the new 'B47' 2.0-litre diesel, which replaces the 'N47', is also more powerful – albeit marginally – than the engine it supersedes. BMW has thusly acquired some cake, and consumed it.
The all-new 'TwinPower' turbocharged diesel, which features a single variable-geometry turbocharger – despite what its name suggests – utilises BMW's latest 'modular' design, entailing a 500cc displacement per cylinder.
Other changes compared to the previous 518d version of the N47 include a higher-pressure common rail injection system, which now operates at 2000 bar as opposed to 1600 bar, and new injectors. These upgrades grant more precise fuel metering and better atomisation, resulting in a more efficient combustion cycle.
There are also myriad other tweaks. At low engine speeds and loads the pump's flow can be throttled back, for example, cutting the power required to drive it and improving overall efficiency.
The net result of all these upgrades is a hike of 7bhp, taking total output to 148bhp. The claimed average economy rises from 62mpg to 64.2mpg, while CO2 emissions drop from 119g/km to 115g/km. Torque remains unchanged however, at 266lb ft.
Fractional gains at best, admittedly, but as VED, company car tax and fuel costs become ever more prominent concerns, and consumers are oft considering downsizing into a smaller car, every little helps in order to maintain the competitiveness of the larger saloons.
Some may be somewhat disappointed to see the new engine retain the rear-mounted and often-problematic timing chain assembly of its predecessor, however; alas the company has had to retain it in order to grant the required bonnet clearance to meet pedestrian crash regulations – which was also the original reason for that design choice. Hopefully, by now, any potential issues have long been engineered out.
What's it like?
We tested a 518d in 'Luxury' specification, a mid-grade trim, with the optional paddle-shifted eight-speed torque convertor automatic and variable damper control – all of which would set you back £35,735.
This, it appears, is a particularly fine combination to opt for. Firstly, you get the slick-shifting, easy-going ZF eight-speed automatic, the wide ranging ratios of which make good use of the diesel's output.
Secondly, besides vast amounts of kit, this trim level equips the 5-series with 18-inch alloy wheels and tyres with a substantial amount of sidewall. Consequently the 5-series rides in a pliant, cosseting fashion that befits its executive saloon nature.
Lastly, and wrapping up the package neatly, the addition of the variable damper control gives the 5-series a wider-ranging breadth of talent than the standard 5-series. A new Comfort+ mode delivers a smoother ride than was possible previously, or, if desired, a Sport mode offers improved responses, minimised body roll and better comfort in high-speed cornering situations.
Is the 518d's engine capable of summing up the kind of performance and refinement that a luxury saloon necessitates though? Well, almost. The 0-62mph sprint is dispatched in a sensible 9.4sec, and in-gear acceleration proves swift enough to not be an annoyance. Above 1500rpm the diesel pulls with comparative vigour, up until around 3500rpm, after which its performance tails off.
Fortunately, despite the narrow 2000rpm spread of power, the sheer number of gear ratios on offer means progress is always swift and the diesel is always kept turning within its favoured range of crank speed. This is beneficial for both the engine and the driver, as worked hard the diesel engine is predictably noisy after 3000rpm – or at full throttle – but the rapid gear changes usually keep it below that speed.
Driven in a sensible fashion, however, or once up to cruising speeds, the engine is quiet and – unlike the BMW X3 – there's no persistent light diesel clatter in the background. The only oddity is that the ZF gearbox is very keen to get into higher gears, for efficiency reasons, which can lead to the engine being laboured somewhat. Once the revs drop below 1500rpm an audible low-frequency drone fills the cabin and a light vibration can be felt; drop down a gear – from seventh to sixth at 30mph, for example – and smoothness and silence is instantly restored.
The engine is otherwise refined, barring its full-throttle, rev-counter roaming vocality – although the swift-acting stop-start system does serve to intermittently remind you that it's definitely a diesel, with the momentary silence and then eruption of noise highlighting how much quieter a petrol would be.
Predictably the BMW also appears to struggle to meet its claimed economy figures. BMW states an average of 64.2mpg but during testing our example averaged 40mpg, after a mix of driving. Adopting a pedestrian, unswerving gait on the motorway may permit you to achieve headier heights but, if you're considering a 518d, we'd suggest you take 40mpg as the baseline and anything above will be a bonus. Either way this means you'll revel in a potential range of upwards of 600 miles.
All in all, the 518d is a reassuringly competent – and quietly satisfying – car to drive, particularly in the specification tested. It corners with aplomb, with plenty of front-end grip and well weighted, precise steering, and there's plenty of traction and stopping power on offer. Its high standards of body control and smooth ride make even fast cross-country driving both comfortable and rewarding, too. It's one of those cars that proves adept in pretty much any situation, a car that you'd be happy to see waiting for you in an airport car park at the end of a long day or at the start of a trek across some Welsh highlands.
Inside little has changed; it's still as comfortable, quiet and as well designed as ever. Admittedly the design of the interior isn't as cohesive or modern-looking as that of, say, the Audi A6, but it's still smartly styled – and there's plenty of room in the cabin and the boot alike.
Luxury trim models feature a lot of equipment as well, helping justify the nigh-on £35k list price – which may otherwise seem a lot for a four-cylinder diesel saloon. The standard SE model on which the Luxury is based features dual-zone climate, Bluetooth connectivity, a USB port, DAB, a 6.5-inch colour screen, Xenon headlights, leather trim, tyre pressure monitoring, automatic lights and wipers, parking sensors and an auto-dimming rear view mirror.
Opting for the Luxury specification, however, expands on this further with a 20GB hard disc drive-based media system, myriad upgraded trims and detail parts, the BMW Professional Media system with sat-nav, a sports multi-function steering wheel and voice control.
Should I buy one?
In the right specification, as seemingly tested here, then the 518d is a genuinely good car. It's an ideal choice if you want an economical, comfortable, rear-drive luxury saloon.
For company car drivers the 518d, in this configuration, will cost those in 40 per cent tax band £225 a month. Admittedly that does make it more expensive than the similarly specified and impressively competent Audi A6 Ultra, which cost £195 a month, but some may be willing to pay that premium for the BMW's rear-drive layout.
Those not fussed by powertrain layout and willing to accept a slight compromise in ride quality, however, would be recommended to look closely at the aforementioned Audi A6 Ultra. Its four-cylinder diesel is quieter, it has a better interior and it's more powerful.
Many may want to also seriously consider paying the £1700 premium – although the company car costs are very similar – for the new 520d. Besides being fractionally more efficient, no doubt due to its more powerful diesel being less laboured, it just feels like the sweeter overall package.
The 520d's also much faster, completing the 0-62mph sprint in 7.7sec compared to 9.4sec, that fraction more competent and capable, and that mite more refined, all of which makes it a more gratifying car to drive and to live with – but the 518d is by no means the poor relation.
BMW 5-series 518d Luxury saloon
Price £35,735; 0-62mph 9.4sec; Top speed 134mph; Economy 64.2mpg (combined); CO2 115g/km; Kerb weight 1700kg; Engine 4 cyls, 1995cc, turbocharged diesel; Power 148bhp at 4000rpm; Torque 266lb ft between 1750-2500rpm; Gearbox 8-spd automatic with paddles