Diesel coupes offer an appealing mix of style, sporty driving and efficiency that won’t whack you in the wallet when it comes to running costs. And the latest mid-size two-door to join the fray is the facelifted BMW 4 Series. Facelifted is the operative word, because the changes to the 4 Series are minimal and centre around tweaked headlights and tail-lamps and new front and rear bumpers. In the battle of the 2.0-litre diesel coupes it was the Audi A5 that came out on top when it met Mercedes’ C-Class Coupe at the end of last year, so it’s this car the 4 Series has to beat. The winner will marry sharp design and handling with decent straight-line performance, but this shouldn’t be at the expense of efficiency or usability. Head-to-head Model: BMW 420d xDrive M Sport auto Audi A5 2.0 TDI S line S tronic Price: £39,595 £38,965 Engine: 2.0-litre 4cyl turbodiesel 2.0-litre 4cyl turbodiesel Power/torque: 187bhp/400Nm 187bhp/400Nm Transmission: Eight-speed, automatic four-wheel drive Seven-speed dual-clutch, automatic front-wheel drive 0-60mph 7.2 seconds 7.4 seconds Top speed: 144mph 148mph Test economy: 42.1mpg 44.4mpg CO2/tax: 125g/km/£140 111g/km/£140 Options: Metallic paint (£645) Metallic paint (£645), 19-inch alloy wheels (£900), storage package (£175), privacy glass (£375), Technology pack (£1,395), flat-bottomed steering wheel (£100) BMW 4 Series 36 • For: Chassis balance, improved infotainment, xDrive traction.

Chassis balance, improved infotainment, xDrive traction. • Against: Doesn’t feel as advanced as A5 inside, pricey options, subtle styling updates. The BMW 4 Series is a sportier proposition than its 3 Series saloon sibling, so in an effort to increase fun from behind the wheel and response to the driver’s inputs, BMW has altered this facelifted 4 Series’ chassis settings.

The 420d was also quicker in-gear thanks to an extra ratio in its eight-speed automatic box. It shifts quickly and smoothly, but it’s not quite as sharp or responsive to a pull of the paddle as Audi’s dual-clutch unit. This showed between 30 and 70mph through the gears, where the A5 was four-tenths faster. 36 Inside, like the styling and chassis developments, BMW has taken an evolutionary approach with some very subtle updates. The firm’s latest iDrive infotainment system features, while there’s the option of a new digital Multifunction Instrument Display to match the A5’s Virtual Cockpit. It’s not quite as convincing, though. Quality is good, with soft-touch plastics lining the dash featuring some imitation double stitching to make it look like leather. All of the interior controls feel solid, while the driving position is more natural than the A5’s. However, the cabin just doesn’t feel quite as classy or as hi-tech as the Audi’s. Testers’ notes: • Infotainment: Biggest changes on 4 Series focus on the display, which has more connectivity and a sharper screen.

Biggest changes on 4 Series focus on the display, which has more connectivity and a sharper screen. • iDrive: BMW’s operating system is easy to get along with, but dial is awkwardly positioned.

BMW’s operating system is easy to get along with, but dial is awkwardly positioned. • Dials: Instruments have been updated, or you can add hi-tech dials as an option. Audi A5 36 • For: Build quality, smooth-shifting gearbox, lots of tech available.

Build quality, smooth-shifting gearbox, lots of tech available. • Against: Anonymous styling, not as much fun as 4 Series, gear ratios.

The latest Audi A5 Coupe doesn’t look much different to its predecessor, but under the classy and understated exterior, it’s all new. It’s based on the brand’s MLB scalable platform, and it’s lighter, faster and more efficient than both the model it replaces and the revised 4 Series. Even so, it wasn’t able to make this advantage pay at the track, where it had to give best to the BMW. Without the benefit of four-wheel drive, the A5 scrabbled from 0-60mph in 7.4 seconds, which was two-tenths slower than the 420d. The Audi also trailed during the in-gear tests, where its twin-clutch transmission was hobbled by its combination of fewer and more widely spread ratios. For instance, the box wouldn’t even let us complete the 50-70mph test in seventh. The A5 managed 9.9 seconds in sixth while the BMW took 7.5 in seventh and 5.8 in sixth. 36 Still, the Audi’s 187bhp 2.0-litre TDI diesel is smoother and more refined than its rival’s unit. And while the seven-speed twin-clutch gearbox’s ratios are poorly chosen for UK roads, with an extremely tall top gear, it shifts seamlessly in auto mode and responds promptly to the wheel-mounted paddles. That said, for many buyers, the slick and precise six-speed manual will be a better choice as it’s good to use and makes for more relaxed progress once under way.