The Mercedes-Benz 300 SEL, part of the W126 S-Class range produced from September 1985 to August 1991, represented a significant evolution of Mercedes-Benz’s flagship sedan. This variant, equipped with a 3.0-liter inline-six engine producing 188 horsepower and paired with a four-speed automatic transmission, occupied a middle ground within the W126 lineup, offering a balance of performance, luxury, and fuel efficiency. The “SEL” designation signified the long-wheelbase version, prioritizing rear passenger comfort. This facelifted W126, introduced in 1985, featured subtle but important revisions to the exterior and interior, solidifying its position as a benchmark for luxury automobiles.
Technical Specifications
| Brand | Mercedes-Benz |
| Model | S-class |
| Generation | S-class SEL (V126, facelift 1985) |
| Type (Engine) | 300 SEL (188 Hp) Automatic |
| Start of production | September, 1985 |
| End of production | August, 1991 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Fuel consumption (urban) | 13.5 l/100 km (17.4 US mpg, 20.9 UK mpg, 7.4 km/l) |
| Fuel consumption (extra urban) | 9.1 l/100 km (25.8 US mpg, 31 UK mpg, 11 km/l) |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 9.1 sec |
| Acceleration 0 – 62 mph | 9.1 sec |
| Acceleration 0 – 60 mph | 8.6 sec |
| Maximum speed | 205 km/h (127.38 mph) |
| Weight-to-power ratio | 8.2 kg/Hp, 121.3 Hp/tonne |
| Weight-to-torque ratio | 6 kg/Nm, 167.7 Nm/tonne |
| Power | 188 Hp @ 5700 rpm |
| Power per litre | 63.5 Hp/l |
| Torque | 260 Nm @ 4400 rpm (191.77 lb.-ft. @ 4400 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | M 103 E 30 / 103.981 |
| Engine displacement | 2962 cm3 (180.75 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 88.5 mm (3.48 in.) |
| Piston Stroke | 80.25 mm (3.16 in.) |
| Compression ratio | 9.2:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | SOHC |
| Engine oil capacity | 6 l (6.34 US qt | 5.28 UK qt) |
| Coolant | 8 l (8.45 US qt | 7.04 UK qt) |
| Kerb Weight | 1550 kg (3417.17 lbs.) |
| Max. weight | 2070 kg (4563.57 lbs.) |
| Max load | 520 kg (1146.4 lbs.) |
| Fuel tank capacity | 90 l (23.78 US gal | 19.8 UK gal) |
| Length | 5160 mm (203.15 in.) |
| Width | 1820 mm (71.65 in.) |
| Height | 1441 mm (56.73 in.) |
| Wheelbase | 3070 mm (120.87 in.) |
| Front track | 1555 mm (61.22 in.) |
| Rear track | 1527 mm (60.12 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 | Ventilated discs |
| Rear brakes | Disc |
| Steering type | Cone worm with recirculation balls |
| Power steering | Hydraulic Steering |
| Tires size | Front wheel tires: 205/65 R15Rear wheel tires: 205/65 R15 |
| Wheel rims size | Front wheel rims: 7J x 15Rear wheel rims: 7J x 15 |
Powertrain & Engine Architecture
The 300 SEL’s engine, designated the M103 E 30 (engine code 103.981), was a 2.962-liter (180.75 cubic inches) inline-six cylinder engine. This engine featured a single overhead camshaft (SOHC) design and utilized Bosch K-Jetronic multi-port fuel injection, a sophisticated system for its time that provided precise fuel delivery. The M103 was known for its smoothness and durability. The four-speed automatic transmission, a common unit in Mercedes-Benz vehicles of the era, was designed for comfortable cruising rather than aggressive acceleration. It featured a torque converter for smooth engagement and a relatively conservative gear ratio spread, prioritizing fuel economy and refinement over outright performance.
Driving Characteristics
The 300 SEL Automatic offered a refined and comfortable driving experience. While not a sports sedan, the 188 horsepower engine provided adequate power for highway cruising and passing maneuvers. Acceleration from 0 to 60 mph took approximately 8.6-9.1 seconds, depending on testing conditions. The automatic transmission, while smooth, did result in some power loss compared to the available five-speed manual transmission. The gear ratios were optimized for relaxed driving, meaning the engine didn’t rev as high or feel as responsive as in the manual versions. The long wheelbase and sophisticated suspension provided a comfortable ride, absorbing bumps and imperfections in the road effectively.
Equipment & Trim Levels
The 300 SEL came standard with a comprehensive list of features expected of a luxury sedan in the mid-1980s. These included power windows, power locks, central locking, air conditioning, and a high-quality sound system. Interior upholstery was typically cloth, but leather was available as an option. Wood trim adorned the dashboard and door panels, adding to the luxurious ambiance. Optional extras included a sunroof, heated seats, and a more advanced audio system. The SEL designation meant a longer wheelbase, translating to increased rear legroom, making it a popular choice for chauffeur-driven executives or families prioritizing rear passenger comfort.
Chassis & Braking
The W126 S-Class featured a robust chassis with independent suspension all around. The front suspension utilized double wishbones, while the rear employed a trailing arm setup. This configuration provided a good balance of ride comfort and handling. The 300 SEL was equipped with ventilated disc brakes at the front and solid disc brakes at the rear, providing adequate stopping power for the vehicle’s weight and performance. Hydraulic power steering was standard, making maneuvering at low speeds easier. Stabilizer bars were fitted front and rear to reduce body roll during cornering.
Market Reception & Comparison
The 300 SEL Automatic was generally well-received by automotive critics. It was praised for its comfortable ride, refined interior, and build quality. However, some critics noted that the automatic transmission dulled the engine’s performance compared to the manual version. Compared to the higher-end 560 SEL, the 300 SEL offered a more affordable entry point into the S-Class range, while still providing a luxurious experience. It also offered better fuel economy than the V8-powered models. Against competitors like the BMW 735i and Audi 100, the 300 SEL was often seen as offering a more comfortable and refined experience, albeit with slightly less sporting handling.
Legacy
The M103 engine, found in the 300 SEL, is known for its reliability and longevity. With proper maintenance, these engines can accumulate high mileage without major issues. The four-speed automatic transmission is also generally reliable, although it may require servicing over time. Today, the W126 S-Class, including the 300 SEL, is gaining popularity among classic car enthusiasts. Well-maintained examples are becoming increasingly collectible, appreciated for their timeless design, build quality, and comfortable driving experience. While parts availability can be a challenge, a dedicated community of enthusiasts and suppliers ensures that these iconic Mercedes-Benz sedans can be kept on the road for years to come.
