The Mercedes-Benz 420 SEL, part of the W126 S-Class range, represented a significant evolution in luxury sedan design and engineering when it was introduced in September 1987, continuing through October 1991. This facelifted version of the W126, distinguished by its integrated bumpers and updated styling cues, offered a blend of performance, comfort, and advanced technology for its time. The 420 SEL, equipped with a 4.2-liter V8 engine and a four-speed automatic transmission, occupied a sweet spot in the lineup, providing ample power without the outright expense of the flagship 560 SEL. It was positioned as a premium offering, appealing to buyers who desired a sophisticated and capable grand tourer.
Technical Specifications
| Brand | Mercedes-Benz |
| Model | S-class |
| Generation | S-class SEL (V126, facelift 1985) |
| Type (Engine) | 420 SEL V8 CAT (224 Hp) Automatic |
| Start of production | September, 1987 |
| End of production | October, 1991 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Fuel consumption (urban) | 15.4 l/100 km (15.3 US mpg, 18.3 UK mpg, 6.5 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 | 8.3 sec |
| Acceleration 0 – 62 mph | 8.3 sec |
| Acceleration 0 – 60 mph | 7.9 sec |
| Maximum speed | 220 km/h (136.7 mph) |
| Weight-to-power ratio | 7.4 kg/Hp, 134.9 Hp/tonne |
| Weight-to-torque ratio | 5.1 kg/Nm, 195.8 Nm/tonne |
| Power | 224 Hp @ 5400 rpm |
| Power per litre | 53.4 Hp/l |
| Torque | 325 Nm @ 4000 rpm (239.71 lb.-ft. @ 4000 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | M 116 E 42 / 116.965 |
| Engine displacement | 4196 cm3 (256.06 cu. in.) |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 92 mm (3.62 in.) |
| Piston Stroke | 78.9 mm (3.11 in.) |
| Compression ratio | 10:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | SOHC |
| Engine oil capacity | 8 l (8.45 US qt | 7.04 UK qt) |
| Coolant | 12.5 l (13.21 US qt | 11 UK qt) |
| Kerb Weight | 1660 kg (3659.67 lbs.) |
| Max. weight | 2180 kg (4806.08 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 |
| Assisting systems | ABS (Anti-lock braking system) |
| 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 420 SEL was the M116 E 42 engine, a 4.2-liter (4196 cc) naturally aspirated V8. This engine, a cornerstone of Mercedes-Benz’s engineering prowess, featured a cast-iron block and aluminum cylinder heads. It employed a single overhead camshaft (SOHC) design with two valves per cylinder. Fuel delivery was handled by a Bosch K-Jetronic multi-port fuel injection system, known for its reliability and precise metering. The engine produced 224 horsepower at 5400 rpm and 325 Nm (239.71 lb-ft) of torque at 4000 rpm. The four-speed automatic transmission, a robust unit for its time, was designed to provide smooth and comfortable shifts, prioritizing a refined driving experience over outright performance. It was a hydraulic controlled transmission, lacking the electronic controls found in later models.
Driving Characteristics
The 420 SEL Automatic offered a distinctly grand touring experience. While not as overtly sporty as some of its competitors, it provided ample power for effortless cruising and confident overtaking. The automatic transmission, while smooth, did result in some power loss compared to the five-speed manual option available on other W126 models. Acceleration from 0 to 60 mph took approximately 7.9 seconds, and it could reach a top speed of 220 km/h (136.7 mph). The gear ratios were tuned for relaxed highway driving, with a focus on minimizing engine revs at cruising speeds. The car felt substantial and planted on the road, offering a comfortable and secure ride, but it wasn’t particularly nimble in tight corners.
Equipment & Trim Levels
The 420 SEL came standard with a comprehensive list of features befitting its luxury status. These included power windows, power locks, a sunroof, leather upholstery, and climate control. Wood trim adorned the interior, adding to the sense of opulence. Optional extras included a premium sound system, heated seats, and a self-leveling suspension system. The interior layout was classic Mercedes-Benz, emphasizing functionality and understated elegance. The dashboard featured a comprehensive array of gauges, providing the driver with detailed information about the vehicle’s performance.
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 420 SEL was equipped with ventilated disc brakes at the front and solid disc brakes at the rear. An Anti-lock Braking System (ABS) was standard, enhancing safety and control during hard braking. The steering was a recirculating ball system with hydraulic power assistance, providing a comfortable and precise driving experience.
Market Reception & Comparison
The 420 SEL was generally well-received by automotive critics. It was praised for its comfortable ride, refined interior, and powerful engine. However, some critics noted that the automatic transmission dulled the driving experience compared to the manual option. Compared to the 300 SEL, the 420 SEL offered significantly more power and performance. The 560 SEL, with its larger 5.6-liter V8, provided even greater performance but came at a higher price point. Fuel economy was a concern for some, with the 420 SEL consuming around 15.4 liters per 100 kilometers in urban driving.
Legacy
The M116 engine, found in the 420 SEL, 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 420 SEL, in particular, represents a sweet spot in the lineup, offering a balance of performance, luxury, and relative affordability in the used car market. While parts availability can be a challenge, the robust construction of the vehicle ensures that it remains a viable and enjoyable classic for years to come.
