The Mercedes-Benz R-Class Long (V251) R 320 CDI V6 4MATIC G-TRONIC, produced from 2007 to 2009, represented a unique offering in the luxury vehicle segment. Positioned as a spacious, versatile vehicle blending elements of a sport utility vehicle (SUV), minivan, and station wagon, the R-Class aimed to provide a comfortable and practical alternative to traditional luxury cars. The “Long” designation indicates an extended wheelbase version, offering increased passenger space, particularly in the second and third rows. This specific R 320 CDI variant, equipped with a 3.0-liter turbocharged diesel V6 engine and a 7-speed automatic transmission, was a key model within the R-Class lineup, targeting buyers seeking a balance of performance, fuel efficiency, and all-weather capability.
Technical Specifications
| Brand | Mercedes-Benz |
| Model | R-Class |
| Generation | R-Class Long (V251) |
| Type (Engine) | R 320 CDI V6 (224 Hp) 4MATIC G-TRONIC |
| Start of production | 2007 |
| End of production | 2009 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Station wagon (estate) |
| Seats | 5-7 |
| Doors | 5 |
| Fuel consumption (combined) | 9.3 l/100 km (25.3 US mpg, 30.4 UK mpg, 10.8 km/l) |
| CO2 emissions | 246 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 8.8 sec |
| Acceleration 0 – 62 mph | 8.8 sec |
| Acceleration 0 – 60 mph | 8.4 sec |
| Maximum speed | 222 km/h (137.94 mph) |
| Emission standard | Euro 5 |
| Weight-to-power ratio | 10.2 kg/Hp, 97.6 Hp/tonne |
| Weight-to-torque ratio | 4.5 kg/Nm, 222.2 Nm/tonne |
| Power | 224 Hp |
| Power per litre | 75 Hp/l |
| Torque | 510 Nm (376.16 lb.-ft.) |
| Maximum engine speed | 4500 rpm |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | OM 642.950 |
| Engine displacement | 2987 cm3 (182.28 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | V-engine |
| Cylinder Bore | 83 mm (3.27 in.) |
| Piston Stroke | 92 mm (3.62 in.) |
| Compression ratio | 16.5:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | Turbocharger, Intercooler |
| Engine oil capacity | 8.5 l (8.98 US qt | 7.48 UK qt) |
| Coolant | 10.1 l (10.67 US qt | 8.89 UK qt) |
| Kerb Weight | 2295 kg (5059.61 lbs.) |
| Max. weight | 2895 kg (6382.38 lbs.) |
| Max load | 600 kg (1322.77 lbs.) |
| Trunk (boot) space – maximum | 2385 l (84.23 cu. ft.) |
| Fuel tank capacity | 80 l (21.13 US gal | 17.6 UK gal) |
| Max. roof load | 100 kg (220.46 lbs.) |
| Permitted trailer load with brakes (12%) | 2100 kg (4629.71 lbs.) |
| Permitted trailer load without brakes | 750 kg (1653.47 lbs.) |
| Length | 5157 mm (203.03 in.) |
| Width | 1922 mm (75.67 in.) |
| Height | 1659 mm (65.31 in.) |
| Wheelbase | 3215 mm (126.57 in.) |
| Drive wheel | All wheel drive (4×4) |
| Number of gears and type of gearbox | 7 gears, automatic transmission G-TRONIC |
| Front suspension | Double wishbone |
| Rear suspension | Independent multi-link spring suspension with stabilizer |
| Front brakes | Disc |
| Rear brakes | Disc |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Hydraulic Steering |
| Tires size | 235/65 R17 |
| Wheel rims size | 7.5J x 17 |
Powertrain & Engine Architecture
The heart of the R 320 CDI is the OM 642.950 3.0-liter V6 diesel engine. This engine, a mainstay in many Mercedes-Benz vehicles of the era, utilizes a common rail direct injection system, delivering fuel at extremely high pressure for optimized combustion. A variable geometry turbocharger with an intercooler further enhances performance and efficiency. The engine produces 224 horsepower and a substantial 510 Nm (376 lb-ft) of torque. The 7G-TRONIC automatic transmission, a seven-speed unit, was paired with this engine. This transmission is known for its smooth shifting and ability to keep the engine in its optimal power band. The 7G-TRONIC features a torque converter lock-up clutch that engages in most gears, improving fuel economy. The engine’s longitudinal mounting and the 4MATIC all-wheel-drive system contribute to balanced handling and traction.
Driving Characteristics
The R 320 CDI offered a refined driving experience, prioritizing comfort and stability over outright sportiness. The 3.0-liter diesel provided ample torque, enabling brisk acceleration despite the vehicle’s considerable weight. The 0-60 mph time of around 8.4 seconds was respectable for a large, luxurious vehicle. The 7-speed automatic transmission contributed to smooth gear changes, and the 4MATIC system provided confident handling in various weather conditions. Compared to the R 350 (gasoline V6) or the higher-performance R 500 (V8), the R 320 CDI prioritized fuel economy and low-end torque. While the gasoline engines offered quicker acceleration, the diesel provided superior fuel efficiency and a more relaxed driving experience, particularly on long journeys. The automatic transmission, while smooth, wasn’t as responsive as the available manual transmission in some European markets.
Equipment & Trim Levels
The R 320 CDI Long typically came well-equipped with standard features including leather upholstery, dual-zone automatic climate control, power-adjustable front seats with memory function, a premium audio system, and a sunroof. Safety features included ABS, traction control, stability control, and multiple airbags. Optional extras included a rear-seat entertainment system, navigation system, adaptive cruise control, and parking assist. Interior trim options varied, allowing buyers to customize the cabin to their preferences. The long wheelbase version offered either six or seven-passenger seating configurations, with the third-row seats being relatively comfortable for adults on shorter trips.
Chassis & Braking
The R-Class Long featured a robust chassis designed to handle the vehicle’s weight and provide a comfortable ride. The front suspension utilized a double wishbone design, while the rear employed an independent multi-link setup with a stabilizer bar. This configuration aimed to minimize body roll and provide a stable platform for cornering. The braking system consisted of ventilated disc brakes on all four wheels, coupled with ABS and electronic brake-force distribution. The R 320 CDI’s weight necessitated a capable braking system, and the discs provided adequate stopping power.
Market Reception & Comparison
The Mercedes-Benz R-Class, despite its innovative design, faced a lukewarm reception in the US market. Critics often questioned its styling and positioning, finding it difficult to categorize. The R 320 CDI, however, was generally praised for its fuel efficiency and comfortable ride. Compared to other luxury SUVs and crossovers of the time, the R-Class offered a unique blend of space, luxury, and fuel economy. However, its unconventional appearance and higher price point limited its appeal. The diesel variant, in particular, was favored by those prioritizing long-distance comfort and fuel savings.
Legacy
The OM 642 engine family, including the OM 642.950 found in the R 320 CDI, is known for its durability and reliability when properly maintained. While diesel engines can be susceptible to issues related to the fuel injection system and particulate filter, these engines generally prove robust with regular servicing. On the used car market, the R 320 CDI represents a relatively affordable entry point into the Mercedes-Benz luxury segment. However, potential buyers should be aware of the potential maintenance costs associated with a diesel engine and the complexity of the vehicle’s electronic systems. The R-Class, while not a commercial success, remains a unique and interesting vehicle, showcasing Mercedes-Benz’s willingness to experiment with new vehicle concepts.
