The BMW X3 (G45) 40d, introduced in April 2025, represents a significant iteration of BMW’s popular compact luxury Sports Activity Vehicle (SAV). This variant, equipped with a 3.0-liter inline-six diesel engine and a 48-volt mild hybrid system, occupies a mid-to-upper position within the G45 X3 lineup, offering a blend of performance, efficiency, and technology. It builds upon the foundation of the G45 platform, shared with other BMW models like the X4, and aims to compete with premium SUVs from Audi, Mercedes-Benz, and Volvo. The 40d trim is positioned above the entry-level 20d and 30i models, offering a substantial power upgrade and a more refined driving experience, while remaining below the performance-oriented M40i.
Technical Specifications
| Brand | BMW |
| Model | X3 |
| Generation | X3 (G45) |
| Type (Engine) | 40d (303 Hp) Mild Hybrid xDrive Steptronic |
| Start of production | April, 2025 |
| Powertrain Architecture | MHEV (Mild Hybrid Electric Vehicle) |
| Body type | SAV |
| Seats | 5 |
| Doors | 5 |
| Combined fuel consumption (WLTP) | 6.2-6.7 l/100 km (37.9 – 35.1 US mpg, 45.6 – 42.2 UK mpg, 16.1 – 14.9 km/l) |
| CO2 emissions (WLTP) | 162-177 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 | 245 km/h (152.24 mph) |
| Emission standard | Euro 6e |
| Weight-to-power ratio | 6.5 kg/Hp, 153.4 Hp/tonne |
| Weight-to-torque ratio | 2.9 kg/Nm, 339.2 Nm/tonne |
| Gross battery capacity | 0.9 kWh |
| Battery voltage | 48 V |
| Battery technology | Lithium-ion (Li-Ion) |
| Battery location | Under the trunk |
| Electric motor power | 18 Hp |
| Electric motor Torque | 200 Nm (147.51 lb.-ft.) |
| Electric motor location | Between the combustion engine and the transmission |
| Electric motor type | Synchronous |
| System power | 303 Hp |
| System torque | 670 Nm (494.17 lb.-ft.) |
| Power | 286 Hp @ 4000 rpm |
| Torque | 650 Nm @ 1500-2500 rpm (479.42 lb.-ft. @ 1500-2500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | B57 |
| 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.) |
| Number of valves per cylinder | 4 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | Twin-power turbo, Intercooler |
| Valvetrain | DOHC |
| Kerb Weight | 1975 kg (4354.13 lbs.) |
| Max. weight | 2620 kg (5776.11 lbs.) |
| Max load | 645 kg (1421.98 lbs.) |
| Trunk (boot) space – minimum | 570 l (20.13 cu. ft.) |
| Trunk (boot) space – maximum | 1700 l (60.03 cu. ft.) |
| Fuel tank capacity | 60 l (15.85 US gal | 13.2 UK gal) |
| AdBlue tank | 21.8 l (5.76 US gal | 4.8 UK gal) |
| Max. roof load | 100 kg (220.46 lbs.) |
| Permitted trailer load with brakes (12%) | 2500 kg (5511.56 lbs.) |
| Permitted trailer load without brakes | 750 kg (1653.47 lbs.) |
| Permitted towbar download | 100 kg (220.46 lbs.) |
| Length | 4755 mm (187.2 in.) |
| Width | 1920 mm (75.59 in.) |
| Width including mirrors | 2132 mm (83.94 in.) |
| Height | 1660 mm (65.35 in.) |
| Wheelbase | 2865 mm (112.8 in.) |
| Front track | 1618-1636 mm (63.7 – 64.41 in.) |
| Rear (Back) track | 1623-1681 mm (63.9 – 66.18 in.) |
| Front overhang | 880 mm (34.65 in.) |
| Rear overhang | 1010 mm (39.76 in.) |
| Ride height (ground clearance) | 216 mm (8.5 in.) |
| Minimum turning circle (turning diameter) | 12.2 m (40.03 ft.) |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
| Number of gears and type of gearbox | 8 gears, automatic transmission Steptronic |
Powertrain & Engine Architecture
At the heart of the X3 40d lies the BMW B57D30 inline-six diesel engine. This engine, a member of the modular BMW engine family, benefits from extensive refinement over previous generations. It utilizes a sophisticated diesel commonrail fuel injection system, delivering precise fuel metering for optimal combustion. The B57 features a twin-scroll turbocharger with variable geometry turbine (VGT) technology, enhancing responsiveness and minimizing turbo lag. The 48V mild hybrid system adds a 18 hp electric motor integrated into the drivetrain, providing a power boost during acceleration and enabling smoother start-stop operation. This system also allows for coasting with the engine switched off, further improving fuel efficiency. The engine is longitudinally mounted, driving all four wheels through BMW’s xDrive all-wheel-drive system and an 8-speed Steptronic automatic transmission. The Steptronic transmission is known for its smooth and quick shifts, and it adapts to the driver’s style.
Driving Characteristics
The X3 40d delivers a compelling driving experience, characterized by strong acceleration and confident handling. The 670 Nm (494 lb-ft) of system torque, available from a low 1500-2500 rpm, provides effortless overtaking and a relaxed cruising experience. The 0-60 mph sprint is dispatched in approximately 5.1 seconds. The 8-speed automatic transmission is well-tuned, offering seamless gear changes and contributing to the overall refinement. Compared to the 20d, the 40d offers a significant performance advantage, while the M40i provides even more power but at the cost of fuel economy. The mild hybrid system contributes to a smoother and more responsive feel, particularly during initial acceleration.
Equipment & Trim Levels
The X3 40d typically comes well-equipped as standard. Key features include BMW’s Live Cockpit Professional, a fully digital instrument cluster and infotainment system, leather upholstery, automatic climate control, and a comprehensive suite of driver-assistance systems such as lane departure warning and collision mitigation. Optional extras include a premium sound system, panoramic sunroof, adaptive suspension, and various interior trim options. The specific standard equipment can vary depending on the market and package selections.
Chassis & Braking
The X3 40d utilizes a robust chassis with a spring strut front suspension and an independent multi-link rear suspension, both incorporating stabilizer bars to minimize body roll. The suspension is tuned to provide a balance between comfort and handling. Braking is handled by ventilated discs on all four wheels, providing ample stopping power. The xDrive all-wheel-drive system intelligently distributes torque between the front and rear axles, optimizing traction in various driving conditions.
Market Reception & Comparison
The X3 40d has generally received positive reviews from automotive critics. It is praised for its powerful and efficient engine, refined driving dynamics, and luxurious interior. Compared to its competitors, the X3 40d often stands out for its engaging driving experience and advanced technology. Fuel economy is competitive for its class, with the mild hybrid system contributing to improved efficiency. Reliability has been generally good, although some owners have reported minor issues with the infotainment system.
Legacy
The B57 engine family has proven to be a durable and reliable powerplant, and the X3 40d is expected to hold its value well in the used car market. The combination of a powerful diesel engine, mild hybrid technology, and BMW’s renowned build quality makes it an attractive option for buyers seeking a premium compact SUV. As with any modern vehicle, regular maintenance is crucial to ensure long-term reliability. The 48V system, while adding complexity, is generally considered robust and well-engineered.
