The BMW 6 Series Convertible (F12) 640d xDrive Steptronic, produced from 2012 to 2015, represents a compelling blend of performance, luxury, and efficiency within the F12 generation of BMW’s flagship convertible. Positioned as a mid-to-high range offering in the 6 Series lineup, the 640d catered to buyers seeking a sophisticated grand tourer with strong diesel power and all-wheel drive capability. It occupied a space between the entry-level 630d and the more performance-focused 650i models, offering a unique proposition for those prioritizing torque and fuel economy without sacrificing BMW’s renowned driving dynamics. The F12 6 Series itself was a successor to the E64 generation, aiming to recapture the classic BMW convertible experience with a more modern and technologically advanced package.
Technical Specifications
| Brand | BMW |
| Model | 6 Series |
| Generation | 6 Series Convertible (F12) |
| Type (Engine) | 640d (313 Hp) xDrive Steptronic |
| Start of production | 2012 |
| End of production | 2015 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (urban) | 7.1-7.3 l/100 km (33.1 – 32.2 US mpg, 39.8 – 38.7 UK mpg, 14.1 – 13.7 km/l) |
| Fuel consumption (extra urban) | 5.1-5.2 l/100 km (46.1 – 45.2 US mpg, 55.4 – 54.3 UK mpg, 19.6 – 19.2 km/l) |
| Fuel consumption (combined) | 5.9-6.0 l/100 km (39.9 – 39.2 US mpg, 47.9 – 47.1 UK mpg, 16.9 – 16.7 km/l) |
| CO2 emissions | 154-158 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 5.4 sec |
| Acceleration 0 – 62 mph | 5.4 sec |
| Acceleration 0 – 60 mph | 5.1 sec |
| Maximum speed | 250 km/h (155.34 mph) |
| Emission standard | Euro 6 |
| Weight-to-power ratio | 6.2 kg/Hp, 162.2 Hp/tonne |
| Weight-to-torque ratio | 3.1 kg/Nm, 326.4 Nm/tonne |
| Power | 313 Hp @ 4400 rpm |
| Power per litre | 104.6 Hp/l |
| Torque | 630 Nm @ 1500-2500 rpm (464.66 lb.-ft. @ 1500-2500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | N57D30B |
| Engine displacement | 2993 cm3 (182.64 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 84 mm (3.31 in.) |
| Piston Stroke | 90 mm (3.54 in.) |
| Compression ratio | 16.5:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | Twin-power turbo, Intercooler |
| Engine oil capacity | 6.5 l (6.87 US qt | 5.72 UK qt) |
| Coolant | 8 l (8.45 US qt | 7.04 UK qt) |
| Kerb Weight | 1930 kg (4254.92 lbs.) |
| Max. weight | 2440 kg (5379.28 lbs.) |
| Max load | 510 kg (1124.36 lbs.) |
| Trunk (boot) space – minimum | 300 l (10.59 cu. ft.) |
| Trunk (boot) space – maximum | 350 l (12.36 cu. ft.) |
| Fuel tank capacity | 70 l (18.49 US gal | 15.4 UK gal) |
| Length | 4894 mm (192.68 in.) |
| Width | 1894 mm (74.57 in.) |
| Height | 1365 mm (53.74 in.) |
| Wheelbase | 2855 mm (112.4 in.) |
| Front track | 1600 mm (62.99 in.) |
| Rear (Back) track | 1665 mm (65.55 in.) |
| Ride height (ground clearance) | 123 mm (4.84 in.) |
| Drag coefficient (Cd) | 0.31 |
| Minimum turning circle | 11.7 m (38.39 ft.) |
| Drive wheel | All wheel drive (4×4) |
| Number of gears and type of gearbox | 8 gears, automatic transmission Steptronic |
| Front suspension | Double wishbone |
| Rear suspension | Independent multi-link suspension |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
Powertrain & Engine Architecture
The heart of the 640d xDrive Steptronic is BMW’s N57D30B inline-six diesel engine. This engine, a member of the widely-respected N57 family, utilizes a common-rail direct injection system operating at extremely high pressures to optimize combustion efficiency and reduce emissions. The N57D30B features a variable geometry turbocharger (VGT) and an intercooler, working in tandem to deliver a broad torque curve and responsive power delivery. The engine’s 3.0-liter displacement produces 313 horsepower at 4,400 rpm and a substantial 630 Nm (464.66 lb-ft) of torque between 1,500 and 2,500 rpm. This torque output is a key characteristic of the 640d, providing effortless acceleration and strong in-gear performance. The engine is paired with BMW’s 8-speed Steptronic automatic transmission, known for its smooth shifts and intelligent programming. The ‘Steptronic’ designation indicates the inclusion of shift paddles, allowing for manual gear selection when desired. The xDrive all-wheel-drive system distributes power between the front and rear axles as needed, enhancing traction and stability in all weather conditions.
Driving Characteristics
The 640d xDrive Steptronic delivers a refined and comfortable driving experience. The abundant torque from the diesel engine provides strong acceleration from low speeds, making it well-suited for both city driving and long-distance cruising. While not as overtly sporty as the 650i, the 640d offers ample power for spirited driving, with the 0-60 mph sprint taking approximately 5.1 seconds. The 8-speed automatic transmission contributes to the smooth and effortless feel, seamlessly shifting gears to keep the engine in its optimal power band. The xDrive system provides excellent grip and stability, inspiring confidence in various driving conditions. Compared to the 630d, the 640d offers a noticeable performance upgrade, while remaining more fuel-efficient than the 650i. The gear ratios are tuned for a balance of acceleration and fuel economy, prioritizing mid-range punch over outright top-end speed.
Equipment & Trim Levels
The 640d xDrive Steptronic came standard with a comprehensive array of luxury features. Interior appointments typically included leather upholstery, power-adjustable seats with memory function, a premium sound system, and a navigation system. Standard safety features included multiple airbags, anti-lock brakes, stability control, and traction control. Optional extras included features such as active steering, adaptive cruise control, a head-up display, and upgraded interior trim options. The convertible top was a fully automatic retractable hardtop, providing a secure and insulated cabin environment when closed. Trim levels were relatively streamlined, with most customization occurring through individual options rather than distinct packages.
Chassis & Braking
The F12 6 Series Convertible featured a sophisticated chassis designed to balance comfort and handling. The front suspension utilized a double wishbone design, while the rear suspension employed an independent multi-link setup. This configuration provided a smooth ride and precise handling characteristics. The 640d xDrive Steptronic was equipped with ventilated disc brakes on all four wheels, providing ample stopping power. The braking system was enhanced by ABS (Anti-lock Braking System) and electronic brakeforce distribution. The steering system was a rack-and-pinion setup with electric power assistance, offering precise and responsive steering feel.
Market Reception & Comparison
The 640d xDrive Steptronic was generally well-received by automotive critics. It was praised for its strong performance, refined ride, and excellent fuel economy. The diesel engine was noted for its quiet operation and smooth power delivery. Compared to its siblings, the 640d offered a compelling alternative for buyers who prioritized torque and efficiency over outright horsepower. While the 650i provided a more exhilarating driving experience, the 640d offered a more practical and economical option without sacrificing BMW’s core values of luxury and performance. Fuel economy figures consistently hovered around 39.9-39.2 US mpg in combined driving, making it a relatively efficient grand tourer.
Legacy
The N57D30B engine has proven to be a robust and reliable powerplant, with many examples exceeding high mileage with proper maintenance. The 8-speed Steptronic transmission is also known for its durability. However, like any modern diesel engine, the 640d requires regular servicing and attention to potential issues such as diesel particulate filter (DPF) regeneration and fuel injector maintenance. In the used car market, the F12 640d xDrive Steptronic represents a good value proposition for buyers seeking a luxurious and capable convertible with strong performance and reasonable running costs. Its blend of performance, efficiency, and all-weather capability continues to make it an appealing choice for discerning drivers.
