The BMW 6 Series Convertible (F12) 640d Steptronic, produced from 2011 to 2015, represents a compelling blend of luxury, performance, and efficiency within the broader F12 6 Series range. Positioned as a mid-to-upper tier offering, the 640d catered to buyers seeking the prestige of the 6 Series convertible experience with the added benefit of a modern diesel powertrain. It occupied a space between the entry-level 630d and the higher-performance 650i models, appealing to those prioritizing fuel economy and torque delivery without sacrificing a refined driving experience. This variant was primarily marketed in Europe and other regions where diesel engines are prevalent, offering a sophisticated alternative to gasoline-powered competitors.
Technical Specifications
| Brand | BMW |
| Model | 6 Series |
| Generation | 6 Series Convertible (F12) |
| Type (Engine) | 640d (313 Hp) Steptronic |
| Start of production | 2011 |
| End of production | 2015 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (urban) | 6.8 l/100 km (34.6 US mpg, 41.5 UK mpg, 14.7 km/l) |
| Fuel consumption (extra urban) | 4.9 l/100 km (48 US mpg, 57.6 UK mpg, 20.4 km/l) |
| Fuel consumption (combined) | 5.6 l/100 km (42 US mpg, 50.4 UK mpg, 17.9 km/l) |
| CO2 emissions | 147-149 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 5.6 sec |
| Acceleration 0 – 62 mph | 5.6 sec |
| Acceleration 0 – 60 mph | 5.3 sec |
| Maximum speed | 250 km/h (155.34 mph) |
| Emission standard | Euro 5 |
| Weight-to-power ratio | 5.9 kg/Hp, 168.3 Hp/tonne |
| Weight-to-torque ratio | 3 kg/Nm, 338.7 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 | 1860 kg (4100.6 lbs.) |
| Max. weight | 2340 kg (5158.82 lbs.) |
| Max load | 480 kg (1058.22 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.) |
| Drivetrain Architecture | Rear wheel drive |
| Number of gears | 8 |
| Gearbox type | Automatic transmission Steptronic |
| Front suspension | Double wishbone |
| Rear suspension | Double wishbone |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Electric Steering |
| Tires size | 225/55 R17; 245/45 R18; 275/45 R18; 245/40 R19; 275/35 R19 |
| Wheel rims size | 8J x 17; 8J x 18; 9J x 18; 8.5J x 19; 9J x 19 |
Powertrain & Engine Architecture
The heart of the 640d Steptronic is BMW’s N57D30B inline-six diesel engine. This 3.0-liter engine utilizes a sophisticated common-rail direct injection system, delivering fuel at extremely high pressures for optimized combustion. The N57 engine family is renowned for its efficiency and durability. The 640d specifically benefits from a twin-turbocharger setup – a smaller turbo for quick response at low RPMs and a larger turbo for sustained power at higher speeds. An intercooler further enhances performance by cooling the compressed intake air. The engine produces 313 horsepower at 4400 rpm and a substantial 630 Nm (464.66 lb.-ft.) of torque between 1500 and 2500 rpm. This broad torque curve is a hallmark of diesel engines and contributes to the 640d’s effortless acceleration. The engine is paired with BMW’s 8-speed Steptronic automatic transmission, known for its smooth shifts and intelligent programming. This transmission allows for both fully automatic operation and manual gear selection via steering wheel-mounted paddles.
Driving Characteristics
The 640d Steptronic delivers a distinctly grand touring experience. The abundant low-end torque makes for relaxed cruising and effortless overtaking. While not as overtly sporty as the 650i, the 640d offers more than adequate performance, achieving 0-60 mph in approximately 5.3 seconds. The 8-speed automatic transmission is well-matched to the engine’s characteristics, providing seamless gear changes and contributing to fuel efficiency. The gear ratios are tuned for both acceleration and highway cruising, keeping the engine within its optimal power band. Compared to the 630d, the 640d offers a noticeable performance upgrade, while remaining more economical than the 650i. The weight distribution is well-balanced, contributing to confident handling, although the convertible body structure does introduce some flex compared to the coupe.
Equipment & Trim Levels
The 640d Steptronic typically came well-equipped, reflecting its position in the 6 Series lineup. Standard features included leather upholstery, power-adjustable seats with memory function, a premium sound system, automatic climate control, and BMW’s iDrive infotainment system. Optional extras were plentiful, allowing buyers to personalize their vehicles. These included features like active steering, adaptive suspension, a head-up display, upgraded leather trim, and various driver assistance systems. Interior trim options ranged from wood veneers to aluminum accents, allowing for a customized aesthetic. The convertible top was fully automatic and insulated for quiet operation.
Chassis & Braking
The F12 6 Series Convertible features a double-wishbone suspension setup at both the front and rear axles. This configuration provides a good balance of ride comfort and handling precision. The 640d typically came equipped with ventilated disc brakes on all four wheels, providing ample stopping power. Anti-lock braking system (ABS) and electronic stability control (ESC) were standard safety features. The steering system is a rack-and-pinion setup with electric power assistance, offering precise and responsive steering feel. The chassis was designed to minimize weight and maximize rigidity, although the convertible body structure inherently has less torsional stiffness than a coupe.
Market Reception & Comparison
The 640d Steptronic was generally well-received by automotive critics. It was praised for its refined driving experience, fuel efficiency, and powerful engine. Critics noted that the diesel engine provided a compelling alternative to the gasoline-powered 650i, particularly for drivers who prioritize economy and torque. Compared to the 630d, the 640d offered a significant performance boost without a substantial increase in fuel consumption. Reliability reports suggest that the N57 engine is generally robust, although preventative maintenance is crucial, particularly regarding the diesel particulate filter (DPF).
Legacy
The BMW 6 Series (F12) 640d Steptronic has established itself as a desirable used car option. The N57 engine’s reputation for durability and efficiency continues to attract buyers. However, potential owners should be aware of the maintenance requirements associated with diesel engines, including regular DPF regeneration and potential issues with the fuel injection system. Well-maintained examples of the 640d Steptronic offer a compelling combination of luxury, performance, and fuel economy, making them a popular choice for those seeking a sophisticated grand tourer.
