The drive system: Four new engines giving the ultimate in driving pleasure

Oct 4, 2010
  • Diesel engines: four-cylinder CDI available for the first time; V6 CDI
    is 21% more economical
  • Petrol engines: BlueDIRECT reduces consumption by 25% in the V6
  • Refined: ECO start/stop function for reduced consumption in urban traffic
  • Now as standard: all engines come with enhanced 7G-TRONIC PLUS automatic transmission
Efficiency at the highest level: this is the common characteristic shared by all four engines used in the Mercedes-Benz CLS. All of the engines feature increased performance and torque compared with previous models, while at the same time boasting significantly reduced consumption and CO2 emission levels. The two V6 engines are typical examples: the diesel engine in the CLS 350 CDI
BlueEFFICIENCY now offers an increase in output of 30 kW, yet at an average of 6.0 litres/100 km consumes 21 percent less fuel than its predecessor.
Thanks to third-generation BlueDIRECT injection technology, the V6 petrol engine in the CLS 350 BlueEFFICIENCY is 25 percent more economical than before, despite an increase in maximum output of 10 kW: it now consumes just 6.8 litres per 100 km and matches its diesel counterparts in terms of CO2 emissions at 159 g/100 km, making them the global role models in their performance class. Advances in efficiency which are every bit as impressive are also to be expected of the V8 engines. The CLS 500 BlueEFFICIENCY will become available during the course of the coming year. The CLS will also become available then with 4MATIC all-wheel drive for the first time.
Setting entirely new standards for efficiency in the luxury segment is the CLS 250 CDI BlueEFFICIENCY. Available for the first time in the four-door Coupé, the four-cylinder direct injection diesel engine has already enthralled customers of the E-Class. With an output of 150 kW (204 hp), a top speed of 242 km/h and a full 500 Nm of torque, it provides complete driving pleasure yet will astound you when filling up with its consumption figures comparable to those of a compact car: on average the CLS 250 CDI BlueEFFICIENCY uses 5.1 litres per 100 km, which is equal to CO2 emissions of 134 g/km
In addition to optimisations in the powertrain – all CLS models are fitted with the enhanced 7G-TRONIC PLUS automatic transmission as standard – the
sophisticated ECO start/stop system helps to ensure extreme efficiency even when driving in urban traffic. Like the petrol models in the CLS range, the CLS 250 CDI BlueEFFICIENCY is fitted with this system as standard.
The ultimate diesel: the V6 engine in the CLS 350 CDI
195 kW(265 hp) and 620 Nm of torque: the excellent diesel engine in the CLS 350 CDI BlueEFFICIENCY is now even more powerful and boasts a correspondingly superior performance. The Coupé accelerates to 100 km/h in 6.2 seconds, and has a top speed of 250 km/h. And despite the increase in output of 30 kW and the additional tractive power of 80 Nm, the V6 consumes a fifth less fuel than previously, at 6.0 litres per 100 km.
To achieve this, the Mercedes engineers have basically revised the engine. It now has improved engine management in the form of new-generation control units and new software, new sensors and actuators, and more efficient aftertreatment in the maintenance-free diesel particulate filter system with reduced back-pressure. In addition to more effective cooling of recirculated exhaust gas using a variable bypass valve, the in-engine measures include a reduction of the compression ratio from 17.7:1 to 15.5:1, an optimised VNT turbocharger with low-friction shaft bearings for greater agility and high output, new injection nozzles and revised ducting in the intake tract. A whole package of measures has resulted in substantial fuel savings: these include generally lower in-engine friction (through precision honing of the cylinder walls, amongst other measures), more efficient thermal management, an improved compound oil pump and modified cylinder head cooling. With an engine idling speed of 520 rpm, a new optimum value has also been achieved.
The diesel engines of the new CLS at a glance
Cylinder arrangement / number
Rated output
at [rpm]
Rated torque
at [rpm]
1600 - 1800
1600 - 2400
Fuel consumption combined
[l/100 km]
CO2 emissions combined

Petrol engine with BlueDIRECT: the most efficient form of direct injection
The second generation of direct petrol injection made its debut in the CLS 350 CGI introduced in 2006. The six cylinder unit was the world's first petrol engine with piezo-electric direct injection and spray-guided combustion, and as such achieved a fuel saving of around ten percent compared with its predecessor with port injection.
Now the third generation of direct petrol injection is celebrating its world premiere, this time in the new CLS. Christened BlueDIRECT, this innovation is helping to establish the V-engines of Mercedes-Benz as the world benchmarks, enabling a further reduction of 20 percent in fuel consumption to be achieved solely through in-engine measures. The key data of the CLS 350 BlueEFFICIENCY include: 225 kW/306 hp (plus 10 kW), 370 Nm (plus 5 Nm), fuel consumption of 6.8 litres per 100 km (minus 2.3 litres). The CLS 350 BlueEFFICIENCY accelerates from 0 to 100 km/h in 6.1 seconds, and achieves a top speed of 250 km/h.
The V6 petrol engine with BlueDIRECT technology in the CLS 350 BlueEFFICIENCY differs from its predecessor in the following key areas:
  • 60° cylinder angle and omission of balancer shaft
  • Extended lean-burn operation, lean-burn system with load monitoring from pressure information, new combustion system operating modes
  • Multi-spark ignition
  • Resonance intake manifold
  • Latest generation of piezo injectors
  • Enhanced cooling circuit control and optimisation
  • Enhanced oil circuit control and optimisation
  • Increased output and torque
BlueDIRECT: third-generation direct injection
Direct petrol injection with spray-guided combustion, which Mercedes-Benz was the first car manufacturer to introduce in series production, has been developed further by the engineers into third-generation direct petrol injection with spray-guided combustion. The system pressure is now up to 200 bar and is variably optimised according to the engine's characteristic map. Completely newly developed piezo-electric injectors allow up to five injections per power stroke for the best possible mixture formation, while multi-spark ignition helps to ensure reliable combustion of the mixture. Further details on direct injection can be found in the section "Under the microscope: lean-burn mixture".
While the V6 unit is a naturally-aspirated engine, the new, technically similar
V8 engine, which is due to be introduced during 2011 as the CLS 500 BlueEFFICIENCY, features biturbocharging for the first time, previously only seen in the 12-cylinder engine used in the S-Class. It too has direct injection but was designed for countries without sulphur-free fuel and is therefore run in a homogenous mode through the engine's entire characteristic map. Despite a significantly smaller displacement (4633 cc; previously 5461 cc), the eight-cylinder unit made considerable gains in terms of output (300 kW/408 hp; previously 285 kW/388 hp) and torque (600 Nm; previously 530 Nm). At the same time consumption has been significantly reduced. It is expected to achieve a saving in the region of 25 percent. Further details on the new engine generation can be found in the section "Under the microscope: innovative engine technology".
The petrol engines of the new CLS at a glance
Cylinder arrangement/ number
Rated output
at [rpm]
Rated torque
at [rpm]
3500 - 5250
1800 - 3500
Fuel consumption combined
[l/100 km]
CO2 emissions combined
*provisional figures
ECO start/stop function: significantly reduced consumption in urban traffic
When the car is at a standstill, the engine does not need to be running and therefore does not need to consume fuel. Recognition of this essentially simple fact is behind the ECO start/stop function, which is available for the first time in the CLS with the 7G-TRONIC PLUS automatic transmission. In order to implement the auto start and auto stop function with a very high level of comfort in a Mercedes-Benz, it has been necessary to develop complex control logistics and a series of new or modified components, such as a Hall sensor for the crankshaft and a high-output starter motor. That's because Mercedes drivers should only really notice the forced breaks taken by the engine when they are at the filling station – thanks to consumption figures which are up to eight percent lower in urban traffic and five percent lower in the ECE consumption cycle. In the case of the CLS 250 CDI BlueEFFICIENCY, CLS 350 BlueEFFICIENCY and CLS 500 BlueEFFICIENCY models, the ECO start/stop system is fitted as standard. More details can be found in the section "Under the microscope: ECO start/stop function".
Smaller tank, same range
Because the new CLS models consume significantly less fuel, it has been possible to reduce the filling volume of the fuel tank in the four and six-cylinder models to 59 litres. The 80-litre tank comes as standard on all V8 engines, and is offered as an optional extra on all CLS variants with the 59-litre tank.
7G-TRONIC PLUS automatic transmission available for the first time with the four-cylinder diesel
All CLS models come with the 7G-TRONIC PLUS automatic transmission as
standard, for which the torque converter and main transmission have been developed and improved further with regard to fuel consumption and comfort. The new generation of the torque converter provides an improved dynamic response, better durability and reduced noise and vibration levels thanks to a new hydraulic circuit, as well as enhanced dampers and torque converter housing. The extreme wheel-slip reduction of the torque converter housing, combined with larger mechanical damper de-coupling, helps to reduce consumption significantly. In addition, the gearshift program in ECO mode has been changed in favour of lower engine rpm at cruising speeds.
With friction-optimised bearings and gaskets, as well as a new automatic
transmission oil (FE-ATF) with reduced viscosity combined with an enhanced additive package, the transmission itself also contributes towards reducing consumption. When the cooling limits are observed, the increased service life of the new oil results in new oil change intervals of every 125,000 kilometres (new) instead of once every 50,000 kilometres (old). The improved electrohydraulic assembly of the transmission and the new friction-reducing materials used on certain transmission parts, combined with optimised software, also lead to better shift quality.
The CLS will also be available with 4MATIC all-wheel drive for the first time in the autumn of 2011.
Mercedes-Benz CLS-Class, CLS 350 CDI, engine
Mercedes-Benz CLS-Class, CLS 350 CDI (german version)
Mercedes-Benz CLS-Class, CLS 350
Mercedes-Benz CLS-Class, CLS 350 CDI
Mercedes-Benz CLS-Class, CLS 250 CDI (german version)
Mercedes-Benz CLS-Class, CLS 250 CDI
Mercedes-Benz CLS-Class, CLS 350 (german version)
Mercedes-Benz CLS-Class, CLS 500
Mercedes-Benz CLS-Class, CLS 500 (german version)
Mercedes-Benz CLS-Class: Fuel consumption reduced by up to 25 percent, ECO start/stop function standard on almost all versions.
Mercedes-Benz CLS-Class: Fuel consumption reduced by up to 25 percent, ECO start/stop function standard on almost all versions.
Mercedes-Benz CLS-Class: Fuel consumption reduced by up to 25 percent, ECO start/stop function standard on almost all versions.