The Mercedes-Benz 300 SE CAT, part of the W126 S-Class range produced from August 1985 to October 1991, represented a significant evolution of the flagship sedan. This facelifted version of the W126, internally designated as the SE (Special Equipment) model, aimed to blend luxury, performance, and increasingly stringent emissions standards. The 300 SE CAT, equipped with a 3.0-liter inline-six engine and a four-speed automatic transmission, occupied a middle ground within the S-Class lineup, offering a balance between the more affordable 260 SE and the higher-performance 560 SEC and SEL models. It was primarily marketed towards buyers seeking a refined and comfortable luxury experience with adequate power for highway cruising and city driving.
Technical Specifications
| Brand | Mercedes-Benz |
| Model | S-class |
| Generation | S-class SE (W126, facelift 1985) |
| Type (Engine) | 300 SE CAT (179 Hp) Automatic |
| Start of production | August, 1985 |
| End of production | October, 1991 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Fuel consumption (urban) | 13.9 l/100 km (16.9 US mpg, 20.3 UK mpg, 7.2 km/l) |
| Fuel consumption (extra urban) | 9.4 l/100 km (25 US mpg, 30.1 UK mpg, 10.6 km/l) |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 9.4 sec |
| Acceleration 0 – 62 mph | 9.4 sec |
| Acceleration 0 – 60 mph | 8.9 sec |
| Maximum speed | 200 km/h (124.27 mph) |
| Weight-to-power ratio | 8.5 kg/Hp, 117.8 Hp/tonne |
| Weight-to-torque ratio | 6 kg/Nm, 167.8 Nm/tonne |
| Power | 179 Hp @ 5700 rpm |
| Power per litre | 60.4 Hp/l |
| Torque | 255 Nm @ 4400 rpm (188.08 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 | 1520 kg (3351.03 lbs.) |
| Max. weight | 2040 kg (4497.43 lbs.) |
| Max load | 520 kg (1146.4 lbs.) |
| Fuel tank capacity | 90 l (23.78 US gal | 19.8 UK gal) |
| Length | 5020 mm (197.64 in.) |
| Width | 1820 mm (71.65 in.) |
| Height | 1437 mm (56.57 in.) |
| Wheelbase | 2930 mm (115.35 in.) |
| Front track | 1555 mm (61.22 in.) |
| Rear (Back) 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 heart of the 300 SE CAT was the M103 E 30 engine, a 2,962 cc (180.75 cu in) inline-six cylinder powerplant. This engine featured a single overhead camshaft (SOHC) design and utilized Bosch K-Jetronic multi-port fuel injection, a system known for its reliability and precise fuel delivery. The catalytic converter (“CAT” in the model designation) was a crucial component, designed to reduce harmful emissions and meet increasingly strict environmental regulations. The engine produced 179 horsepower at 5,700 rpm and 255 Nm (188 lb-ft) of torque at 4,400 rpm. The four-speed automatic transmission, a robust unit for its time, was designed to provide smooth and comfortable gear changes. It wasn’t particularly sporty, prioritizing refinement over aggressive shifting.
Driving Characteristics
The 300 SE CAT offered a comfortable and composed driving experience. While not a sports sedan, the engine provided sufficient power for effortless highway cruising and confident acceleration in most situations. The automatic transmission, while smooth, did contribute to a slight reduction in responsiveness compared to the available manual transmission. The gear ratios were geared towards fuel efficiency and relaxed driving, rather than outright performance. Acceleration from 0 to 60 mph took approximately 8.9 seconds, and the top speed was around 124 mph. The emphasis was on providing a serene and luxurious ride, absorbing bumps and imperfections in the road with ease.
Equipment & Trim Levels
The 300 SE CAT came standard with a comprehensive list of features befitting a luxury sedan of its era. These included power windows, central locking, air conditioning, and a high-quality sound system. The interior was typically upholstered in leather, with wood trim adorning the dashboard and door panels. Optional extras included a sunroof, heated seats, and a more advanced audio system. The level of equipment positioned the 300 SE CAT as a well-appointed vehicle, though not as lavishly equipped as the top-of-the-line 560 SEL.
Chassis & Braking
The W126 S-Class featured a robust chassis with independent suspension all around. The front suspension utilized a double wishbone design, while the rear employed a trailing arm setup. This configuration provided a comfortable ride and good handling characteristics. The 300 SE CAT was equipped with ventilated disc brakes at the front and solid disc brakes at the rear, providing adequate stopping power for its weight and performance. Hydraulic power steering was standard, making maneuvering easy and effortless.
Market Reception & Comparison
The 300 SE CAT was generally well-received by automotive critics. It was praised for its comfortable ride, refined interior, and build quality. However, some reviewers noted that the engine, while adequate, lacked the outright performance of the larger-displacement engines offered in other S-Class models. Compared to the 260 SE, the 300 SE CAT offered a noticeable increase in power and refinement. Against the 560 SEL, it represented a more economical option, albeit with less horsepower. Fuel economy was reasonable for a vehicle of its size and class, averaging around 20 mpg combined.
Legacy
The M103 engine, found in the 300 SE CAT, is known for its durability and longevity. With proper maintenance, these engines can reliably exceed 200,000 miles. The W126 S-Class, as a whole, is considered a classic Mercedes-Benz, and well-maintained examples are highly sought after by collectors and enthusiasts. The 300 SE CAT, while not the most powerful or exclusive variant, offers a compelling combination of luxury, reliability, and affordability in the used car market. Parts availability is generally good, although some specific trim pieces can be difficult to find. The car represents a high point in Mercedes-Benz engineering and design, embodying the brand’s commitment to quality and refinement.
