The BMW 6 Series Convertible (F12 LCI), specifically the 640d 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 640d variant occupied a middle ground in the 6 Series lineup, offering a compelling blend of performance, fuel economy, and luxury features, appealing to buyers seeking a sophisticated and capable convertible.
Technical Specifications
| Brand | BMW |
| Model | 6 Series |
| Generation | 6 Series Convertible (F12 LCI, facelift 2015) |
| Type (Engine) | 640d (313 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) | 6.5-6.8 l/100 km (36.2 – 34.6 US mpg, 43.5 – 41.5 UK mpg, 15.4 – 14.7 km/l) |
| Fuel consumption (extra urban) | 5.1-5.5 l/100 km (46.1 – 42.8 US mpg, 55.4 – 51.4 UK mpg, 19.6 – 18.2 km/l) |
| Fuel consumption (combined) | 5.6-6.0 l/100 km (42 – 39.2 US mpg, 50.4 – 47.1 UK mpg, 17.9 – 16.7 km/l) |
| CO2 emissions | 149-158 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 5.3 sec |
| Acceleration 0 – 62 mph | 5.3 sec |
| Acceleration 0 – 60 mph | 5 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 |
| 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) | 0.30 |
| Minimum turning circle | 11.7 m (38.39 ft.) |
| Drive wheel | All wheel drive (4×4) |
| Number of gears | 8 |
| Gearbox type | 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 640d xDrive 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 durability and efficiency. The ‘D30B’ designation indicates a displacement of 3.0 liters and the ‘B’ signifies the modular engine architecture. Crucially, this engine features a twin-turbocharger setup – a smaller turbo for immediate response and a larger turbo for peak power. 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 the N57 engine, providing strong acceleration in virtually any gear.
Power is transmitted to all four wheels via BMW’s xDrive all-wheel-drive system and an eight-speed Steptronic automatic transmission. The Steptronic transmission offers both fully automatic operation and manual gear selection via steering wheel-mounted paddles. The transmission’s gear ratios are tuned to balance performance and fuel efficiency, with taller gears for relaxed cruising and shorter gears for quicker acceleration.
Driving Characteristics
The 640d xDrive Steptronic delivers a refined and effortless driving experience. The abundant torque from the diesel engine provides strong acceleration from low speeds, making it well-suited for both city driving and highway cruising. While not as overtly sporty as the 640i or 650i models, the 640d offers more than adequate performance for most drivers, achieving 0-60 mph in around 5 seconds. The xDrive all-wheel-drive system provides excellent traction in all weather conditions, enhancing stability and confidence. The automatic transmission shifts smoothly and responsively, contributing to the overall sense of refinement. Compared to manual transmission versions of the 640d, the Steptronic automatic prioritizes comfort and ease of use over outright driver engagement.
Equipment & Trim Levels
The 640d xDrive Steptronic typically came well-equipped as standard. Features included leather upholstery, power-adjustable seats with memory function, a premium sound system, navigation, and a host of driver-assistance systems such as parking sensors and automatic climate control. Optional extras included upgraded leather trim, a head-up display, active steering, and various styling packages. The convertible top was fully automatic and could be operated at speeds up to 40 km/h (25 mph). Interior trim options ranged from wood veneers to aluminum accents, allowing buyers to personalize the cabin to their taste.
Chassis & Braking
The F12 6 Series Convertible featured a double-wishbone front suspension and an independent multi-link rear suspension, providing a comfortable yet controlled ride. The suspension was tuned to balance handling and comfort, offering a good compromise between sporty responsiveness and long-distance cruising ability. Braking duties were handled by disc brakes on all four wheels, with ABS (Anti-lock Braking System) and electronic stability control as standard features. The 640d, being a heavier model due to the diesel engine and all-wheel-drive system, often featured slightly uprated brakes compared to the lighter gasoline-powered variants.
Market Reception & Comparison
The 640d xDrive Steptronic was generally well-received by automotive critics. It was praised for its strong performance, excellent fuel economy, and luxurious interior. Compared to the 640i (gasoline), the 640d offered superior fuel efficiency and a broader torque curve, making it a more practical choice for long-distance driving. However, the 640i was often preferred by drivers seeking a more engaging and sporty driving experience. The 650i, with its larger V8 engine, offered even more power but at the expense of fuel economy. The 640d struck a balance between these two extremes, appealing to a wider range of buyers.
Legacy
The N57 engine family, including the N57D30B found in the 640d, has proven to be remarkably reliable. With proper maintenance, these engines can easily exceed 200,000 miles. Common issues, such as diesel particulate filter (DPF) clogging, can be mitigated with regular servicing and occasional highway driving. On the used car market, the 640d xDrive Steptronic represents a compelling value proposition, offering a luxurious and capable convertible at a more affordable price point than newer models. Its blend of performance, efficiency, and refinement continues to make it a desirable choice for buyers seeking a sophisticated grand tourer.
