• Lacklustre 420i and 430i eclipsed by glorious 440i
• Diesel 420d does almost everything you need
• Rapid 435d xDrive is a great all-rounder, but expensive

There’s a choice of seven powerplants here, with a mix of petrol and diesel in four- and six-cylinder, turbocharged form. Gearboxes include a six-speed manual and eight-speed auto.

BMW 4 Series Convertible petrol engines

The entry-level 420i is powered by a four-cylinder, 2.0-litre unit with 184hp at 5,000rpm and 290Nm of torque at 1,350rpm, meaning a 0-62mph time of 8.2 seconds, or 8.4 for the auto. Our experience with this version is that you wait and wait for the power to arrive, and then have to change gear. It’s best avoided.

Better is the 430i, which uses the same engine but produces 252hp at 5,200rpm, and 350Nm at 1,450rpm. This means a faster 0-62mph time of 6.4 seconds (6.3 auto) and a sprightlier feel. It’s still not bristling with excitement but does the job effectively enough.

Best of all though is the straight-six 440i, which sounds like a proper BMW and goes like one too, with 326hp at 5,500rpm and 450Nm at 1,380rpm, and a 0-62mph time of 5.4 seconds. It’s automatic-only but the fast-shifting ‘box rips through its ratios with vigour.

BMW M4 Convertible engine

The performance-focused M4 comes with a 3.0-litre, six-cylinder engine with 431hp and 550Nm of torque.

This twin-turbocharged unit will have the M4 dart its way from 0-62mph in 4.4 seconds with the seven-speed DCT automatic gearbox, or 4.6 seconds with the six-speed manual.

It’s faster than the previous M3 too, helped in part by a 30 percent increase in torque over the old naturally-aspirated V8-engined car. In fact, with access to the full 550Nm of torque at 1,850rpm, this makes for a Jekyll-and-Hyde personality – acting as a relaxed cruiser when you want, without needing to change down a gear too often, or making extremely light work of overtaking in the mid-range.

While a six-speed manual gearbox might be a tempting option for some, it’s not the most satisfying to use; with a slightly notchy gearshift that doesn’t particularly enjoy being rushed.

BMW M4 Competition Package

If you want to up the ante on your M4 a tad further, the Competition Package adds an additional 19hp.

Bringing the total output to 450hp, this drops the 0-62mph time by 0.1 seconds – equating to a time of 4.3 seconds for the DCT gearbox and 4.5 seconds when you manually change gears yourself.

BMW 4 Series Convertible diesel engines

The first rung here (and arguably the best all-rounder) is the 420d, which puts out 190hp at 4,000rpm and 400Nm at 1,750rpm. That means a 0-62mph time of 8.1 seconds (8.0 auto), which isn’t a lot faster than the 420i, but the additional torque of this engine makes it feel considerably more muscular at low revs.

Next up is the six-cylinder 430d, which offers 258hp at 4,000rpm and 560Nm at 1,500rpm, taking just 5.9 seconds to get from 0-62mph. This engine comes in automatic-only and offers a smoother and quieter power delivery than the 420d, which in fairness is also nicely refined.

Top of the tree is the auto and all-wheel drive only 435d xDrive, which answers pretty much any question you could ask of a 4 Series Convertible. Powerful (313hp at 4,400rpm and 630Nm at 1,500rpm), fast (0-62mph takes 5.2 seconds) and surprisingly economical, this engine has the broadest spread of talents, and a price-tag to back it up.

• Heavier and less agile than 4 Series Coupe
• Still a fun car to drive thanks to great chassis
• Steering numb but hefty and accurate enough

Handling is always going to be near the top of the list of priorities for a BMW and the 4 Series Convertible is no different.

While there’s almost always a penalty to pay when lopping the roof off a hard-top car, BMW claims the 4 Series drop-top is 30 percent more rigid than the car it replaced.

That means good things through corners. It’s not quite as agile as the Coupe model, but it’s closer than ever.

Suits a more laid back driving style

The downside of that is extra weight and while the 4 Series does feel suitably composed and sure-footed, it’s not as satisfying to drive fast on a windy road.

There isn’t much feel through the wheel but it’s nicely weighted and accurate enough to encourage enthusiastic driving, although we reckon the 4 Series Convertible suits a more languid approach than its sharper coupe relative.

The cars we tested came with adaptive suspension installed, which allows the driver to swap between Comfort, Sport and Sport+ at the flick of a switch – it works extremely well, offering a broad range of settings from squashy to tied down.

BMW M4 Competition Package handling

The good news here is that, for the most part, the M4 Convertible Competition Package doesn’t feel night-and-day different to the Coupe model.  That weighty roof mechanism and loss in rigidity will mean the limits of this car can be reached far sooner – which is great if you view the M4 as a GT car, but not so much as a pin-sharp sports car.

There’s plenty of grip and far better traction over its soft-top Mercedes-Benz C63 S rival, allowing you to apply power sooner on corner exits. The M locking differential helps out here and gives you much more confidence in using the M4’s power. 

That said, the M4 Convertible does feel a little bit like a blunt tool in the corners. Despite being composed, the steering is artificially heavy in Sport Plus mode, while mid-corner bumps reveal the body’s reduction in rigidity. The brakes are effective though.