The BMW 725tds, produced between 1996 and 1998, was a diesel-powered variant of the E38 generation 7 Series luxury sedan. Positioned as a more fuel-efficient alternative within the 7 Series lineup, it aimed to offer a balance between the prestige of the flagship model and the practicality of a diesel engine, particularly appealing to European buyers where diesel sedans were more common. This model represented BMW’s continued development of diesel technology for its premium vehicles, offering a sophisticated driving experience with improved economy compared to the gasoline-powered counterparts.
Technical Specifications
| Brand | BMW |
| Model | 7 Series |
| Generation | 7 Series (E38) |
| Type (Engine) | 725tds (143 Hp) |
| Start of production | 1996 |
| End of production | 1998 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Fuel consumption (urban) | 11 l/100 km (21.4 US mpg, 25.7 UK mpg, 9.1 km/l) |
| Fuel consumption (extra urban) | 6.2 l/100 km (37.9 US mpg, 45.6 UK mpg, 16.1 km/l) |
| Fuel consumption (combined) | 8 l/100 km (29.4 US mpg, 35.3 UK mpg, 12.5 km/l) |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 11.4 sec |
| Acceleration 0 – 62 mph | 11.4 sec |
| Acceleration 0 – 60 mph | 10.8 sec |
| Maximum speed | 206 km/h (128 mph) |
| Weight-to-power ratio | 12 kg/Hp, 83.6 Hp/tonne |
| Weight-to-torque ratio | 6.1 kg/Nm, 163.7 Nm/tonne |
| Power | 143 Hp @ 4600 rpm |
| Power per litre | 57.3 Hp/l |
| Torque | 280 Nm @ 2200 rpm (206.52 lb.-ft. @ 2200 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | M51D25 |
| Engine displacement | 2497 cm3 (152.38 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 80 mm (3.15 in.) |
| Piston Stroke | 82.8 mm (3.26 in.) |
| Compression ratio | 22:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Precombustion chamber injection |
| Engine aspiration | Turbocharger, Intercooler |
| Valvetrain | OHC |
| Engine oil capacity | 7 l (7.4 US qt | 6.16 UK qt) |
| Coolant | 9.8 l (10.36 US qt | 8.62 UK qt) |
| Kerb Weight | 1710 kg (3769.9 lbs.) |
| Max. weight | 2245 kg (4949.38 lbs.) |
| Max load | 535 kg (1179.47 lbs.) |
| Trunk (boot) space – minimum | 500 l (17.66 cu. ft.) |
| Fuel tank capacity | 85 l (22.45 US gal | 18.7 UK gal) |
| Length | 4984 mm (196.22 in.) |
| Width | 1862 mm (73.31 in.) |
| Height | 1435 mm (56.5 in.) |
| Wheelbase | 2930 mm (115.35 in.) |
| Front track | 1552 mm (61.1 in.) |
| Rear (Back) track | 1568 mm (61.73 in.) |
| Drag coefficient (Cd) | 0.30 |
| Minimum turning circle | 11.6 m (38.06 ft.) |
| Drivetrain Architecture | Rear wheel drive |
| Drive wheel | Rear wheel drive |
| Number of gears | 5 |
| Gearbox type | Manual transmission |
| Front suspension | Coil spring |
| Rear suspension | Inclined Lever |
| Front brakes | Ventilated discs |
| Rear brakes | Disc |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Hydraulic Steering |
| Tires size | 215/60 R16 |
| Wheel rims size | 16 |
Powertrain & Engine Architecture
The heart of the 725tds was the M51D25, a 2.5-liter inline-six diesel engine. This engine utilized precombustion chamber injection, a system common in European diesels of the era, which involved injecting fuel into a small pre-chamber connected to the main combustion chamber. This design promoted more complete combustion and reduced engine noise. A turbocharger with an intercooler was employed to boost power output to 143 horsepower and 280 Nm (206.52 lb.-ft.) of torque. The engine featured an overhead camshaft (OHC) valvetrain with two valves per cylinder. The 5-speed manual transmission was the only gearbox option available for this variant, providing a direct connection between the engine and the rear wheels.
Driving Characteristics
The 725tds offered a distinctly different driving experience compared to the gasoline-powered 7 Series models. While lacking the outright acceleration of its petrol siblings, the diesel engine delivered strong low-end torque, making it well-suited for relaxed cruising and effortless overtaking. The manual transmission allowed for precise control, but the gear ratios were optimized for fuel efficiency rather than sporty performance. Acceleration from 0 to 60 mph took around 10.8 seconds, and the top speed was limited to 128 mph. Compared to the higher-output 740i or 750iL, the 725tds prioritized fuel economy and refinement over raw power.
Equipment & Trim Levels
The 725tds typically came equipped with a respectable level of standard features, befitting its status as a luxury sedan. This included power windows, power locks, air conditioning, and a basic audio system. Interior upholstery was generally cloth, although leather was available as an option. The dashboard layout was consistent with other E38 7 Series models, featuring a wood trim and a clear instrument cluster. Optional extras included a premium sound system, navigation system, heated seats, and a sunroof. The trim level was generally considered a mid-range offering, providing a good balance of features and affordability.
Chassis & Braking
The 725tds shared the same chassis and suspension components as other E38 7 Series models. It featured a coil spring front suspension and an inclined lever rear suspension, designed to provide a comfortable and controlled ride. The braking system consisted of ventilated discs at the front and solid discs at the rear, with ABS (Anti-lock Braking System) as standard. The steering was a rack-and-pinion system with hydraulic power assistance. The vehicle rode on 215/60 R16 tires mounted on 16-inch alloy wheels.
Market Reception & Comparison
The 725tds was primarily aimed at the European market, where diesel engines were more popular in the luxury car segment. Critics generally praised the car’s fuel efficiency and comfortable ride, but some noted its lack of outright performance compared to the gasoline-powered models. Fuel economy figures were around 29.4 US mpg combined, significantly better than the 740i or 750iL. Reliability was generally good, although diesel engines of this era could be susceptible to issues with the fuel injection system and turbocharger. The 725tds offered a more affordable entry point into the E38 7 Series range, appealing to buyers who prioritized economy and practicality.
Legacy
The BMW 725tds represents an important step in BMW’s development of diesel technology for its flagship models. While not as widely recognized as its gasoline-powered counterparts, the 725tds has gained a following among diesel enthusiasts and those seeking a unique and fuel-efficient luxury sedan. The M51D25 engine is known for its durability and relatively simple construction, making it a popular choice for restoration and modification projects. Today, well-maintained examples of the 725tds are sought after by collectors and enthusiasts, offering a glimpse into a bygone era of luxury diesel motoring.
