The Mercedes-Benz R-Class Long (V251) R 300 CDI V6 G-TRONIC, produced from 2009 to 2010, represented a unique offering in the luxury vehicle segment. Positioned as a spacious, versatile, and technologically advanced grand tourer, the R-Class aimed to blend the practicality of an SUV with the driving experience of a sedan. The “Long” designation indicates an extended wheelbase version, primarily aimed at markets desiring increased rear passenger space. This particular R 300 CDI variant, equipped with a 3.0-liter V6 diesel engine and the 7G-TRONIC automatic transmission, served as a mid-range option within the R-Class lineup, offering a balance between performance, fuel efficiency, and refinement. It was primarily sold in European markets where diesel engines were highly favored.
Technical Specifications
| Brand | Mercedes-Benz |
| Model | R-Class |
| Generation | R-Class Long (V251) |
| Type (Engine) | R 300 CDI V6 (190 Hp) G-TRONIC |
| Start of production | 2009 |
| End of production | 2010 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Station wagon (estate) |
| Seats | 5 |
| Doors | 5 |
| Fuel consumption (combined) | 9 l/100 km (26.1 US mpg, 31.4 UK mpg, 11.1 km/l) |
| CO2 emissions | 238 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 9.8 sec |
| Acceleration 0 – 62 mph | 9.8 sec |
| Acceleration 0 – 60 mph | 9.3 sec |
| Maximum speed | 210 km/h (130.49 mph) |
| Emission standard | Euro 5 |
| Weight-to-power ratio | 11.8 kg/Hp, 84.6 Hp/tonne |
| Weight-to-torque ratio | 5.1 kg/Nm, 196 Nm/tonne |
| Power | 190 Hp @ 3800 rpm |
| Power per litre | 63.6 Hp/l |
| Torque | 440 Nm @ 1400-2800 rpm (324.53 lb.-ft. @ 1400-2800 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 |
| Compression ratio | 15.5:1 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | Turbocharger, Intercooler |
| Engine oil capacity | 8.5 l (8.98 US qt | 7.48 UK qt) |
| Coolant capacity | 10.1 l (10.67 US qt | 8.89 UK qt) |
| Kerb Weight | 2245 kg (4949.38 lbs.) |
| Max. weight | 2860 kg (6305.22 lbs.) |
| Max load | 615 kg (1355.84 lbs.) |
| Trunk (boot) space – maximum | 2245 l (79.28 cu. ft.) |
| Fuel tank capacity | 80 l (21.13 US gal | 17.6 UK gal) |
| 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 | 1674 mm (65.91 in.) |
| Wheelbase | 3215 mm (126.57 in.) |
| Front track | 1661 mm (65.39 in.) |
| Rear (Back) track | 1651 mm (65 in.) |
| Minimum turning circle | 12.4 m (40.68 ft.) |
| Drivetrain Architecture | Rear wheel drive |
| 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 | Ventilated discs |
| 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 | 17 |
Powertrain & Engine Architecture
The heart of the R 300 CDI is the OM 642.950 3.0-liter V6 diesel engine. This engine, a mainstay of Mercedes-Benz’s diesel offerings, features a robust cast iron block and aluminum cylinder heads. It utilizes a common rail direct injection system, delivering fuel at extremely high pressures for optimized combustion and reduced emissions. A variable geometry turbocharger with an intercooler further enhances performance and efficiency. The engine produces 190 horsepower at 3800 rpm and a substantial 440 Nm (324.53 lb-ft) of torque between 1400 and 2800 rpm. This broad torque curve is characteristic of diesel engines and contributes to strong acceleration and effortless cruising. The engine also incorporates a diesel particulate filter (DPF) to minimize soot emissions, meeting stringent Euro 5 emission standards.
The engine is mated to Mercedes-Benz’s 7G-TRONIC seven-speed automatic transmission. This transmission is known for its smooth and responsive shifts, contributing to a refined driving experience. The 7G-TRONIC features a torque converter lock-up clutch that engages at higher speeds to improve fuel efficiency. Gear ratios are optimized for both acceleration and highway cruising, providing a balance between performance and economy.
Driving Characteristics
The R 300 CDI Automatic delivers a comfortable and composed driving experience. While not a sports car, the engine’s ample torque provides brisk acceleration, with a 0-60 mph time of around 9.3 seconds. The 7G-TRONIC transmission shifts smoothly and intelligently, selecting the appropriate gear for the driving conditions. Compared to the more powerful R 350 variants, the R 300 CDI offers less outright performance, but its superior fuel economy and relaxed cruising ability make it well-suited for long-distance journeys. The automatic transmission, while convenient, doesn’t offer the same level of driver engagement as a manual gearbox. However, it provides a seamless and effortless driving experience, particularly in urban traffic.
Equipment & Trim Levels
The R 300 CDI Long typically came well-equipped, reflecting its luxury positioning. Standard features included leather upholstery, automatic climate control, a premium audio system, and power-adjustable front seats. Optional extras included a panoramic sunroof, navigation system, rear seat entertainment, and advanced driver-assistance systems such as adaptive cruise control and lane keeping assist. Trim levels varied by market, but generally offered increasing levels of luxury and technology. The extended wheelbase provided generous rear passenger legroom, making it a comfortable choice for families or those frequently carrying passengers.
Chassis & Braking
The R-Class Long features a double wishbone front suspension and an independent multi-link rear suspension with a stabilizer bar. This suspension setup provides a comfortable ride and good handling characteristics. The R 300 CDI is equipped with ventilated disc brakes at the front and solid disc brakes at the rear. Anti-lock braking system (ABS) is standard, enhancing safety and stability during braking. The steering is a hydraulic power-assisted rack and pinion system, providing precise and responsive steering feel.
Market Reception & Comparison
The Mercedes-Benz R-Class, despite its innovative design and luxurious features, never achieved widespread popularity. Critics often cited its unconventional styling and high price tag as drawbacks. The R 300 CDI, however, was generally praised for its fuel efficiency and refined driving experience. Compared to the R 350, the R 300 CDI offered better fuel economy and lower running costs, making it a more practical choice for those prioritizing efficiency. However, the R 350 provided more power and a sportier driving experience. The R 320 CDI, with its more powerful engine, offered a compromise between the two.
Legacy
The OM 642 engine family, including the OM 642.950 found in the R 300 CDI, is known for its durability and reliability. With proper maintenance, these engines can accumulate high mileage without major issues. The 7G-TRONIC transmission is also generally reliable, although some units may require servicing over time. On the used car market, the R-Class Long R 300 CDI represents a relatively affordable entry point into the Mercedes-Benz luxury segment. Its spacious interior, comfortable ride, and fuel-efficient diesel engine make it a practical and appealing choice for those seeking a versatile and refined grand tourer.
