The Mercedes-Benz GL 420 CDI 4MATIC, produced between 2006 and 2009, was a high-performance variant of the first-generation GL (X164) full-size luxury SUV. Positioned as a premium offering within the GL lineup, it catered to buyers seeking a blend of robust diesel power, all-wheel-drive capability, and luxurious appointments. The X164 GL was Mercedes-Benz’s first foray into the full-size SUV segment, aiming to compete with established models like the Cadillac Escalade, Lincoln Navigator, and BMW X5. The 420 CDI, with its powerful V8 diesel engine, represented the top-tier performance option until the introduction of the GL 550.
Technical Specifications
| Brand | Mercedes-Benz |
| Model | GL |
| Generation | GL (X164) |
| Type (Engine) | GL 420 CDI (306 Hp) 4MATIC G-TRONIC |
| Start of production | 2006 |
| End of production | 2009 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | SUV |
| Seats | 5 |
| Doors | 5 |
| Fuel consumption (urban) | 15.6 l/100 km (15.1 US mpg, 18.1 UK mpg, 6.4 km/l) |
| Fuel consumption (extra urban) | 9.2 l/100 km (25.6 US mpg, 30.7 UK mpg, 10.9 km/l) |
| Fuel consumption (combined) | 11.6 l/100 km (20.3 US mpg, 24.4 UK mpg, 8.6 km/l) |
| CO2 emissions | 307 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 7.6 sec |
| Acceleration 0 – 62 mph | 7.6 sec |
| Acceleration 0 – 60 mph | 7.2 sec |
| Maximum speed | 230 km/h (142.92 mph) |
| Emission standard | Euro 4 |
| Weight-to-power ratio | 8.1 kg/Hp, 123.6 Hp/tonne |
| Weight-to-torque ratio | 3.5 kg/Nm, 282.8 Nm/tonne |
| Power | 306 Hp @ 3600 rpm |
| Power per litre | 76.6 Hp/l |
| Torque | 700 Nm @ 2000 rpm (516.29 lb.-ft. @ 2000 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | OM 629.912 |
| Engine displacement | 3996 cm3 (243.85 cu. in.) |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 86 mm (3.39 in.) |
| Piston Stroke | 86 mm (3.39 in.) |
| Compression ratio | 17:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | BiTurbo, Intercooler |
| Valvetrain | DOHC |
| Engine oil capacity | 11.5 l (12.15 US qt, 10.12 UK qt) |
| Kerb Weight | 2475 kg (5456.44 lbs.) |
| Max. weight | 3250 kg (7165.02 lbs.) |
| Max load | 775 kg (1708.58 lbs.) |
| Trunk (boot) space – minimum | 620 l (21.9 cu. ft.) |
| Trunk (boot) space – maximum | 2300 l (81.22 cu. ft.) |
| Fuel tank capacity | 100 l (26.42 US gal, 22 UK gal) |
| Permitted trailer load with brakes (12%) | 3500 kg (7716.18 lbs.) |
| Permitted trailer load without brakes | 750 kg (1653.47 lbs.) |
| Length | 5088 mm (200.31 in.) |
| Width | 1920 mm (75.59 in.) |
| Height | 1840 mm (72.44 in.) |
| Wheelbase | 3075 mm (121.06 in.) |
| Front track | 1645 mm (64.76 in.) |
| Rear (Back) track | 1648 mm (64.88 in.) |
| Drag coefficient (Cd) | 0.37 |
| Minimum turning circle | 12.1 m (39.7 ft.) |
| Drive wheel | All wheel drive (4×4) |
| Number of gears | 7 |
| Gearbox type | automatic transmission G-TRONIC |
| Front suspension | Double wishbone |
| Rear suspension | Independent multi-link suspension |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Cone worm with recirculation balls |
| Power steering | Hydraulic Steering |
| Tires size | 275/55 R19 |
| Wheel rims size | 19 |
Powertrain & Engine Architecture
The heart of the GL 420 CDI is the OM 629.912 4.0-liter V8 diesel engine. This engine utilizes a common rail direct injection system, delivering fuel at extremely high pressure for optimized combustion. The engine is equipped with a sequential bi-turbocharger system, featuring two turbochargers of different sizes. A smaller turbocharger provides quick response at low engine speeds, while a larger turbocharger delivers increased power at higher RPMs. An intercooler further enhances performance by cooling the compressed intake air. The engine boasts a robust 17:1 compression ratio, contributing to its high torque output. The 7G-TRONIC seven-speed automatic transmission, a hallmark of Mercedes-Benz engineering, was standard. This transmission offered smooth and efficient gear changes, contributing to both performance and fuel economy. The transmission was programmed with a focus on comfort and refinement, rather than aggressive sportiness.
Driving Characteristics
The GL 420 CDI offered a compelling driving experience for a vehicle of its size. The 700 Nm (516 lb-ft) of torque, available from just 2000 rpm, provided effortless acceleration and strong pulling power. While not a sports car, the GL 420 CDI could accelerate from 0 to 60 mph in approximately 7.2 seconds. The 7G-TRONIC transmission’s gear ratios were optimized for both highway cruising and towing. Compared to the gasoline-powered GL 450, the 420 CDI offered significantly more torque and better fuel economy. However, the gasoline engine provided a more responsive and higher-revving experience. The 420 CDI also differed from the GL 320 CDI, offering substantially more power and torque, but at a higher price point.
Equipment & Trim Levels
The GL 420 CDI came standard with a comprehensive list of features, befitting its premium positioning. These included leather upholstery, wood trim, dual-zone automatic climate control, a premium sound system, and power-adjustable front seats with memory function. Available options included a rear-seat entertainment system, a panoramic sunroof, and adaptive suspension. The exterior featured chrome accents and distinctive badging to differentiate it from other GL models. The interior design emphasized luxury and comfort, with a focus on high-quality materials and meticulous craftsmanship.
Chassis & Braking
The GL 420 CDI utilized a robust chassis designed to handle the vehicle’s weight and power. It featured a fully independent suspension system, with double wishbones at the front and a multi-link setup at the rear. This suspension configuration provided a comfortable ride and good handling characteristics. Ventilated disc brakes were standard on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) was also standard, enhancing safety and control. The 4MATIC all-wheel-drive system distributed power to all four wheels, providing excellent traction in various driving conditions.
Market Reception & Comparison
The GL 420 CDI was generally well-received by automotive critics. It was praised for its powerful engine, comfortable ride, and luxurious interior. However, some reviewers noted its relatively high price and substantial weight. Compared to the GL 450, the 420 CDI offered superior fuel economy and torque, making it a popular choice for buyers who frequently towed or drove long distances. The GL 320 CDI, while more affordable, lacked the performance of the 420 CDI. Fuel economy, while respectable for a vehicle of its size, was still relatively high at around 20 mpg combined.
Legacy
The OM 629 engine, while robust, is known to require diligent maintenance, particularly regarding the fuel injection system and turbochargers. The 7G-TRONIC transmission is generally reliable, but can be expensive to repair if issues arise. Today, the GL 420 CDI represents a unique offering in the used luxury SUV market. Its combination of diesel power, all-wheel drive, and luxurious features remains appealing to certain buyers. However, potential owners should be prepared for the higher maintenance costs associated with a diesel engine and a complex vehicle like the GL. The X164 GL paved the way for the second-generation GL, establishing Mercedes-Benz as a contender in the full-size luxury SUV segment.
