The BMW 420i Coupe (F32, facelift 2017) with the Steptronic automatic transmission represents a key entry point into the BMW 4 Series lineup during its production run from 2017 to 2020. Positioned as a more accessible alternative to the higher-performance 430i and 440i models, the 420i offered a blend of BMW’s renowned driving dynamics, stylish coupe design, and relatively efficient operation. This variant was primarily aimed at buyers seeking a premium, sporty coupe experience without the higher price tag or increased running costs associated with its more powerful siblings. It built upon the foundation of the F32 4 Series, which itself was a successor to the E92 3 Series Coupe, establishing a distinct identity for the 4 Series as a more style-focused and dynamically engaging offering.
Technical Specifications
| Brand | BMW |
| Model | 4 Series |
| Generation | 4 Series Coupe (F32, facelift 2017) |
| Type (Engine) | 420i (184 Hp) Steptronic |
| Start of production | 2017 |
| End of production | 2020 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Coupe |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (urban) | 7.1-7.6 l/100 km (33.1 – 30.9 US mpg, 39.8 – 37.2 UK mpg, 14.1 – 13.2 km/l) |
| Fuel consumption (extra urban) | 4.5-4.7 l/100 km (52.3 – 50 US mpg, 62.8 – 60.1 UK mpg, 22.2 – 21.3 km/l) |
| Fuel consumption (combined) | 5.5-5.8 l/100 km (42.8 – 40.6 US mpg, 51.4 – 48.7 UK mpg, 18.2 – 17.2 km/l) |
| CO2 emissions | 127-134 g/km |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 7.5 sec |
| Acceleration 0 – 62 mph | 7.5 sec |
| Acceleration 0 – 60 mph | 7.1 sec |
| Maximum speed | 236 km/h (146.64 mph) |
| Emission standard | Euro 6 |
| Weight-to-power ratio | 8.1 kg/Hp, 123.1 Hp/tonne |
| Weight-to-torque ratio | 5.5 kg/Nm, 180.6 Nm/tonne |
| Power | 184 Hp @ 5000 rpm |
| Torque | 270 Nm @ 1350-4600 rpm (199.14 lb.-ft. @ 1350-4600 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | B48B20A |
| Engine displacement | 1998 cm3 (121.93 cu. in.) |
| Number of cylinders | 4 |
| Engine configuration | Inline |
| Cylinder Bore | 82 mm (3.23 in.) |
| Piston Stroke | 94.6 mm (3.72 in.) |
| Compression ratio | 11:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Direct injection |
| Engine aspiration | Twin-power turbo, Intercooler |
| Engine oil capacity | 5.25 l (5.55 US qt | 4.62 UK qt) |
| Coolant | 8.1 l (8.56 US qt | 7.13 UK qt) |
| Kerb Weight | 1495 kg (3295.91 lbs.) |
| Max. weight | 2015 kg (4442.31 lbs.) |
| Max load | 520 kg (1146.4 lbs.) |
| Trunk (boot) space – minimum | 445 l (15.72 cu. ft.) |
| Fuel tank capacity | 60 l (15.85 US gal | 13.2 UK gal) |
| Max. roof load | 75 kg (165.35 lbs.) |
| Permitted trailer load with brakes (12%) | 1500 kg (3306.93 lbs.) |
| Permitted trailer load without brakes | 695 kg (1532.21 lbs.) |
| Permitted towbar download | 75 kg (165.35 lbs.) |
| Length | 4640 mm (182.68 in.) |
| Width | 1825 mm (71.85 in.) |
| Height | 1377 mm (54.21 in.) |
| Wheelbase | 2810 mm (110.63 in.) |
| Front track | 1547 mm (60.91 in.) |
| Rear (Back) track | 1593 mm (62.72 in.) |
| Ride height (ground clearance) | 130 mm (5.12 in.) |
| Drag coefficient (Cd) | 0.29 |
| Minimum turning circle (turning diameter) | 11.3 m (37.07 ft.) |
| Drivetrain Architecture | The Internal combustion engine (ICE) drives the rear wheels of the vehicle. |
| Drive wheel | Rear wheel drive |
| Number of gears and type of gearbox | 8 gears, automatic transmission Steptronic |
| Front suspension | Independent coil spring |
| Rear suspension | Independent multi-link suspension |
| 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 | 225/50 R17; 225/45 R18; 255/40 R18; 225/40 R19; 255/35 R19 |
| Wheel rims size | 7.5J x 17; 8J x 18; 8.5J x 18; 8J x 19; 8.5J x 19 |
Powertrain & Engine Architecture
The heart of the 420i is BMW’s B48B20A 2.0-liter turbocharged inline-four cylinder engine. This engine is a member of BMW’s modular engine family, known for its efficiency and performance. The B48 utilizes direct fuel injection, a single twin-scroll turbocharger, and variable valve timing (VANOS) and valve lift (Valvetronic) technologies to optimize power delivery and fuel economy. The engine produces 184 horsepower at 5,000 rpm and 270 Nm (199 lb-ft) of torque between 1,350 and 4,600 rpm. This torque curve provides good responsiveness in everyday driving situations. The engine is longitudinally mounted, driving the rear wheels. The “Steptronic” transmission is BMW’s name for its 8-speed automatic gearbox. This transmission is known for its smooth shifts and intelligent programming, adapting to driving style and conditions. It features steering wheel-mounted paddle shifters for manual control.
Driving Characteristics
The 420i Steptronic delivers a comfortable and refined driving experience. While not as overtly sporty as the 430i or 440i, it offers ample power for everyday driving and highway cruising. The 8-speed automatic transmission contributes to smooth acceleration and efficient gear changes. The 0-60 mph time of around 7.1 seconds is respectable, but the focus is more on usability than outright speed. Compared to the 6-speed manual version of the 420i, the Steptronic offers greater convenience, particularly in urban traffic. However, some enthusiasts may find the manual transmission more engaging. The gear ratios are tuned for a balance of acceleration and fuel efficiency, with taller gears for relaxed highway cruising.
Equipment & Trim Levels
The 420i Coupe typically came standard with features such as leatherette upholstery, automatic climate control, a 6.5-inch iDrive infotainment system, and a suite of safety features including ABS, stability control, and airbags. Optional extras included leather upholstery, a larger iDrive screen with navigation, a premium sound system, and various driver-assistance systems like lane departure warning and adaptive cruise control. Trim levels varied depending on the market, but generally offered packages that bundled popular options together. Sport Line packages added exterior styling enhancements and sport seats, while Luxury Line packages focused on a more refined interior aesthetic.
Chassis & Braking
The 420i Coupe utilizes a sophisticated chassis design featuring an independent coil spring suspension at the front and an independent multi-link suspension at the rear. This setup provides a good balance of ride comfort and handling precision. The steering is precise and well-weighted, offering good feedback to the driver. Braking duties are handled by ventilated disc brakes on all four wheels, providing ample stopping power. The ABS system helps to prevent wheel lockup during hard braking. The suspension tuning is generally softer than that of the higher-performance 4 Series models, prioritizing comfort over ultimate track performance.
Market Reception & Comparison
The 420i Coupe was generally well-received by automotive critics as a stylish and capable entry-level offering in the 4 Series range. It was praised for its comfortable ride, refined interior, and efficient engine. However, some critics noted that the engine lacked the outright punch of its larger counterparts. Compared to the 430i, the 420i offered a more affordable price point but sacrificed some performance. The 420d (diesel) variant offered similar performance with even better fuel economy, but the 420i appealed to buyers who preferred a gasoline engine. Fuel economy figures of around 42.8 mpg combined were considered competitive for its class.
Legacy
The B48 engine in the 420i has proven to be a relatively reliable unit, although some early models experienced issues with oil leaks and cooling system components. Regular maintenance, including oil changes and coolant flushes, is crucial for long-term reliability. The 8-speed Steptronic transmission is also generally reliable, but it’s important to ensure that it’s serviced according to BMW’s recommendations. On the used car market, the 420i Coupe represents a good value proposition for buyers seeking a stylish and well-equipped coupe. Its combination of performance, efficiency, and comfort makes it a compelling choice in its price range. The F32 4 Series, including the 420i, has established itself as a popular and desirable modern classic.
