The BMW 6 Series Convertible (F12 LCI), specifically the 640i xDrive Steptronic model produced from 2015 to 2018, represents a refined iteration of BMW’s luxury open-top grand tourer. This facelift, designated LCI (Life Cycle Impulse) by BMW, brought styling updates, improved efficiency, and enhanced technology to the F12 generation, which itself was built on the F06 platform. The 640i xDrive Steptronic occupied a mid-to-upper position within the 6 Series Convertible lineup, offering a balance of performance, luxury, and all-weather capability thanks to its xDrive all-wheel-drive system. It served as a compelling alternative to rivals like the Mercedes-Benz E-Class Cabriolet and the Porsche 911 Cabriolet, appealing to buyers seeking a sophisticated and powerful convertible experience.
Technical Specifications
| Brand | BMW |
| Model | 6 Series |
| Generation | 6 Series Convertible (F12 LCI, facelift 2015) |
| Type (Engine) | 640i (320 Hp) xDrive Steptronic |
| Start of production | 2015 |
| End of production | 2018 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (urban) | 11.2-11.7 l/100 km (21 – 20.1 US mpg, 25.2 – 24.1 UK mpg, 8.9 – 8.5 km/l) |
| Fuel consumption (extra urban) | 6.2-6.4 l/100 km (37.9 – 36.8 US mpg, 45.6 – 44.1 UK mpg, 16.1 – 15.6 km/l) |
| Fuel consumption (combined) | 8.0-8.4 l/100 km (29.4 – 28 US mpg, 35.3 – 33.6 UK mpg, 12.5 – 11.9 km/l) |
| CO2 emissions | 187-195 g/km |
| Fuel Type | Petrol (Gasoline) |
| 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 | 5.9 kg/Hp, 169.3 Hp/tonne |
| Weight-to-torque ratio | 4.2 kg/Nm, 238.1 Nm/tonne |
| Power | 320 Hp @ 5800-6000 rpm |
| Power per litre | 107.4 Hp/l |
| Torque | 450 Nm @ 1300-4500 rpm (331.9 lb.-ft. @ 1300-4500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | N55B30A |
| Engine displacement | 2979 cm3 (181.79 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 84 mm (3.31 in.) |
| Piston Stroke | 89.6 mm (3.53 in.) |
| Compression ratio | 10.2:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Direct injection |
| Engine aspiration | Twin-power turbo, Intercooler |
| Engine oil capacity | 6.5 l (6.87 US qt | 5.72 UK qt) |
| Coolant | 9.3 l (9.83 US qt | 8.18 UK qt) |
| Kerb Weight | 1890 kg (4166.74 lbs.) |
| Max. weight | 2390 kg (5269.05 lbs.) |
| Max load | 500 kg (1102.31 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 (turning diameter) | 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 | Disc |
| Rear brakes | Disc |
| 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; 245/35 R20; 275/30 R20 |
| Wheel rims size | 8J x 17; 8J x 18; 9J x 18; 8.5J x 19; 9J x 19; 8.5J x 20; 9J x 20 |
Powertrain & Engine Architecture
The heart of the 640i xDrive Steptronic is BMW’s N55B30A inline-six engine. This 3.0-liter (2979 cc) engine is a direct-injection, twin-turbocharged powerplant known for its smooth power delivery and responsiveness. The N55 utilizes a single twin-scroll turbocharger, an intercooler, and Double-VANOS (variable valve timing) and Valvetronic (variable valve lift) technologies to optimize performance and efficiency. The engine produces 320 horsepower at 5800-6000 rpm and 450 Nm (331.9 lb-ft) of torque between 1300 and 4500 rpm. This broad torque curve contributes to strong acceleration in real-world driving conditions. The engine is paired with BMW’s 8-speed Steptronic automatic transmission, which offers smooth and quick shifts. The xDrive all-wheel-drive system intelligently distributes power between the front and rear axles, enhancing traction and stability, particularly in adverse weather conditions.
Driving Characteristics
The 640i xDrive Steptronic delivers a refined and engaging driving experience. While not as overtly sporty as some of its competitors, the combination of the turbocharged inline-six and the eight-speed automatic provides ample power for confident overtaking and comfortable cruising. The xDrive system contributes to excellent grip and stability, inspiring confidence in various driving conditions. The 0-60 mph acceleration time of around 5.1 seconds is respectable for a luxury convertible. Compared to the 650i models with their larger V8 engines, the 640i offers a more balanced driving experience, prioritizing efficiency and everyday usability without sacrificing significant performance. The automatic transmission is well-tuned, providing seamless gear changes and responsive kickdowns. The steering is precise and well-weighted, offering a good connection to the road.
Equipment & Trim Levels
The 640i xDrive Steptronic came standard with a comprehensive list of features, befitting its luxury positioning. These included leather upholstery, power-adjustable seats with memory function, a premium sound system, a navigation system, automatic climate control, and a host of safety features such as ABS, stability control, and multiple airbags. Optional extras included features like active steering, adaptive suspension, a head-up display, and various interior trim options. The convertible top was a fully automatic soft top, available in several colors, and could be operated at speeds up to 40 km/h (25 mph). Interior trim options ranged from standard wood veneers to more exclusive carbon fiber or aluminum accents.
Chassis & Braking
The F12 6 Series Convertible features a double-wishbone front suspension and an independent multi-link rear suspension, providing a comfortable and controlled ride. The suspension geometry is tuned to minimize body roll and maximize stability. The 640i xDrive Steptronic is equipped with disc brakes on all four wheels, providing ample stopping power. ABS (Anti-lock Braking System) is standard, along with electronic brake-force distribution and brake assist. The steering system utilizes an electric power steering rack and pinion, offering precise and responsive steering feel.
Market Reception & Comparison
The 640i xDrive Steptronic was generally well-received by automotive critics. It was praised for its refined engine, comfortable ride, and luxurious interior. The xDrive all-wheel-drive system was also highlighted as a significant advantage, particularly in regions with inclement weather. Compared to the 650i models, the 640i offered a more affordable entry point into the 6 Series Convertible range, while still providing a compelling level of performance and luxury. Fuel economy was considered reasonable for a vehicle of its size and performance, with combined fuel consumption figures ranging from 8.0 to 8.4 l/100 km. Reliability has been generally good, although some owners have reported minor issues with electronic components.
Legacy
The BMW 6 Series Convertible (F12 LCI) 640i xDrive Steptronic has established itself as a desirable used car. The N55 engine is known for its durability and relatively straightforward maintenance. While the convertible top mechanism can require occasional attention, overall reliability has been good. The combination of performance, luxury, and all-weather capability continues to appeal to buyers seeking a sophisticated and enjoyable open-top driving experience. The F12 generation, and specifically the 640i xDrive Steptronic, represents a high point in BMW’s convertible heritage, offering a blend of engineering excellence and timeless design.
