The Mercedes-Benz W123 300 D Turbodiesel, produced from 1982 to 1985 for the US market, represents a pivotal point in the evolution of the mid-size luxury sedan. As the diesel variant of the highly successful W123 series, it offered American buyers a blend of German engineering, fuel efficiency, and robust build quality. The W123, in general, was a significant model for Mercedes-Benz, solidifying their reputation for safety, reliability, and understated elegance. The 300 D Turbodiesel specifically addressed the growing demand for fuel-conscious vehicles in the wake of the 1970s energy crises, while still delivering a premium driving experience.
The Mercedes-Benz W123 300 D Turbodiesel
The W123 series, manufactured between 1976 and 1985, succeeded the W114 and W115 models. It was a global car, but specifications and engine options varied significantly depending on the target market. The US-spec 300 D Turbodiesel was tailored to meet American emissions regulations and driver preferences. It distinguished itself with its turbocharged diesel engine, offering improved performance compared to naturally aspirated diesel counterparts. The W123 was a popular choice for those seeking a durable, comfortable, and economical vehicle, and many examples remain on the road today, a testament to their longevity.
Engine & Performance
The heart of the W123 300 D Turbodiesel is its 3.0-liter inline-five cylinder diesel engine, designated OM 617 D 30 A / 617.952. This engine produced 125 horsepower at 4350 rpm and 250 Nm (184.39 lb.-ft.) of torque at 2400 rpm. The addition of a turbocharger significantly enhanced the engine’s power output and responsiveness, addressing a common criticism of diesel engines of the era – a lack of acceleration. While not a sports car, the 300 D Turbodiesel offered respectable performance for its time, achieving a 0-60 mph time of approximately 13.3 seconds and a top speed of 170 km/h (105.63 mph). The engine employed precombustion chamber injection, a common diesel technology of the period, and featured a single overhead camshaft (SOHC) valvetrain. The engine’s longitudinal front-engine layout contributed to balanced weight distribution. The engine oil capacity is 9.5 liters (10.04 US qt | 8.36 UK qt) and requires a specific oil specification. The cooling system holds 11 liters (11.62 US qt | 9.68 UK qt) of coolant.
Design & Features
The W123 300 D Turbodiesel is a four-door sedan with a classic, understated Mercedes-Benz design. Its body style prioritized practicality and comfort over flamboyant aesthetics. The interior was well-appointed for its time, featuring durable materials and a focus on ergonomics. Safety was also a key consideration, with features like crumple zones and a robust passenger cell. While not equipped with the advanced safety systems of modern vehicles, the W123 offered a significant improvement in safety compared to earlier models. The car’s dimensions – 4848 mm (190.87 in) in length, 1786 mm (70.31 in) in width, and 1438 mm (56.61 in) in height – provided ample space for passengers and luggage. The wheelbase measured 2795 mm (110.04 in), contributing to a comfortable ride. The car rides on 195/70 R14 tires on 6J x 14 inch wheel rims. The W123’s build quality was renowned, with a focus on durability and longevity, making it a popular choice for high-mileage drivers.
Technical Specifications
| Brand | Mercedes-Benz |
| Model | W123 |
| Generation | W123 |
| Type | 300 D Turbodiesel (125 Hp) Automatic (USA) |
| Start of production | October, 1982 |
| End of production | August, 1985 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 14 sec |
| Acceleration 0 – 62 mph | 14 sec |
| Acceleration 0 – 60 mph | 13.3 sec |
| Maximum speed | 170 km/h (105.63 mph) |
| Weight-to-power ratio | 13 kg/Hp, 76.9 Hp/tonne |
| Weight-to-torque ratio | 6.5 kg/Nm, 153.8 Nm/tonne |
| Power | 125 Hp @ 4350 rpm |
| Power per litre | 41.7 Hp/l |
| Torque | 250 Nm @ 2400 rpm (184.39 lb.-ft. @ 2400 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | OM 617 D 30 A / 617.952 |
| Engine displacement | 2998 cm3 (182.95 cu. in.) |
| Number of cylinders | 5 |
| Engine configuration | Inline |
| Cylinder Bore | 90.9 mm (3.58 in.) |
| Piston Stroke | 92.4 mm (3.64 in.) |
| Compression ratio | 21.5:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Precombustion chamber injection |
| Engine aspiration | Turbocharger |
| Valvetrain | SOHC |
| Engine oil capacity | 9.5 l (10.04 US qt | 8.36 UK qt) |
| Coolant | 11 l (11.62 US qt | 9.68 UK qt) |
| Kerb Weight | 1625 kg (3582.51 lbs.) |
| Max. weight | 2080 kg (4585.62 lbs.) |
| Max load | 455 kg (1003.1 lbs.) |
| Fuel tank capacity | 80 l (21.13 US gal | 17.6 UK gal) |
| Length | 4848 mm (190.87 in.) |
| Width | 1786 mm (70.31 in.) |
| Height | 1438 mm (56.61 in.) |
| Wheelbase | 2795 mm (110.04 in.) |
| Front track | 1488 mm (58.58 in.) |
| Rear (Back) track | 1446 mm (56.93 in.) |
| 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 | 4 gears, automatic transmission |
| Front suspension | Double wishbone |
| Rear suspension | Trailing arm |
| Front brakes | Disc |
| Rear brakes | Disc |
| Steering type | Cone worm with recirculation balls |
| Power steering | Hydraulic Steering |
| Tires size | Front wheel tires: 195/70 R14Rear wheel tires: 195/70 R14 |
| Wheel rims size | Front wheel rims: 6J x 14Rear wheel rims: 6J x 14 |
