Which is the most reliable model in the Mercedes Benz C Class?

In this article, we answer the questions: Which is the most reliable Mercedes Benz C class model? What are the engine specifications in the most reliable  Mercedes Benz C Class? Which driver assistance systems are present in the Mercedes Benz C Class?

Which is the most reliable model in the Mercedes Benz C Class?

The most reliable model in the Mercedes Benz C class is the 2019 C 300d. Mercedes Benz launched the fourth generation of the C class in 2014 and midway through its life cycle, Mercedes launched the facelift model of the fourth generation. After rectifying the issues in the pre-facelift  C class model, Mercedes Benz updated the front and rear bumper design and high-performance dynamic LED headlights come as standard.

The C class has always been the entry-level model in the sedan segment of Mercedes Benz, it can easily accommodate 5 passengers and more than 450 litres of boot space.  

The fourth generation of the C class is the most reliable since the first generation was launched in 1993 with the model series W202. 

The old generation of the C class had many reliability issues due to malfunctions in the ABS/ESP control unit and abnormal noise from the engine. Mercedes Benz rectified all the reliability issues in the facelift of the Mercedes Benz C class.

Both petrol and diesel engines are available in the 2019 C class facelift but it is the 300d model that is most reliable. Many customers have driven their C class for more than 100,000 km without any issues. The C 300d is also an AMG line model meaning the exterior and interior styling is more sporty and similar to the high-performance version of the C class.

It gets the diamond grille with the AMG logo and AMG 19-inch alloy wheels as standard. The AMG alloy wheels are also designed to reduce the overall drag and also cool the brake pads and brake disc.

Currently, the C class is in its fifth generation with the model series W206 which will be replacing the W205 C class. The W206 also looks more in line with the current design language of Mercedes Benz. The W206 also looks very reliable but it is only launched in limited markets and only time will tell if there are any major reliability concerns in the new generation. 

The C class is mainly manufactured in the Sindelfingen factory in Germany, the Mother factory also ships completely knocked down kits to the Assembly plant in India and China.

What are the engine specifications in the Mercedes Benz C 300d?

The Mercedes Benz C 300d is so reliable because it is powered by the new Mercedes Benz diesel engine OM654. It is an inline 4 cylinder 2.0-litre engine introduced in 2016. Mercedes Benz is using the OM654 in all classes. It can also be mounted sideways for the new generation models like the A, B, GLA, and CLA classes.

The OM654 produces 242 horsepower and 500 Nm of torque. The top speed is 250 kmph and the fuel economy in the combined driving conditions is 5 litres/ 100 km or 40 to 50MPG.

Unlike the predecessor OM651 engine which had a cast-iron engine block, the OM654 uses an aluminium engine block. It makes the OM654 lighter compared to the OM 654. Traditionally, diesel engines have a cast-iron block because the compression pressure can be more than 25 bars. The diesel fuel is also self-igniting fuel and the engines are designed as over square so the pistons and connecting rods need to be strong enough to withstand the additional torque.

However, thanks to the use of the latest manufacturing technology and high-pressure fuel injection system with 8 holes piezo injector and the pistons made up of special aluminium alloy. Mercedes Benz has managed to use an aluminium engine block instead of a cast-iron one. The use of the aluminium crankcase has helped greatly in the weight reduction of the engine. 

The pistons are also made of steel with stepped combustion cavities. The narrow piston compression area allows maximum air efficiency and thereby reduces soot levels. The crankshaft is also forged with a de-axial arrangement of cylinder barrels towards the cold side of the engine.

The OM 654 also uses  NANOSLIDE coating on the cylinder walls. This is an extremely thin coating applied to the inner surface of the cylinder to reduce friction between the piston. Twin-wire arc spraying (TWAS) is used to spray an extremely thin coat of iron-carbon alloy on the cylinder walls.  The friction between the piston and piston rings is reduced by almost 50 per cent.

The OM654 in the C300d is bi turbocharged but instead of using two wastegate type turbochargers, Mercedes Benz uses one variable geometry turbo with an electronic actuator and one wastegate controlled turbocharger. 

The wastegate turbochargers are high-pressure turbochargers and only come into operation at the top end of the engine performance. The boost pressure is controlled by conventional vacuum transducers connected to the wastegate linkage.

The variable geometry turbocharger is a low-pressure turbo meaning it is responsible for providing charged air at low engine speeds. The electronic actuator controls the angle of guide vanes in the turbo and the variable geometry can either direct the exhaust glass flow on the turbine wheel or release it towards the high-speed turbocharger.

The use of variable geometry turbochargers has greatly reduced the components in the charge air intake system. The low-pressure turbocharger never reaches its choke limit when the high-pressure turbocharger kicks in hence, there is no need for an air recirculation bypass flap for the low-pressure turbocharger.

The charge air intercooler is also liquid-cooled, there is an independent secondary coolant pump with its coolant reservoir and electric coolant pump. The intercooler ensures hot changed air is cooled down before reaching the intake manifold.

The OM654 also uses a low-pressure exhaust gas recirculation system and a high-pressure exhaust gas recirculation system with an integrated EGR cooler. Exhaust gas recirculation massively reduces the NOX emissions and OM654 also has selective catalytic reduction with AdBlue injection in the exhaust gas system. The diesel particulate filter ensures no soot particles escape the exhaust system.

Which driver assistance systems are present on the Mercedes Benz C300 d?

The Mercedes Benz C 300d is an AMG line model and it comes with advanced driver assistance systems such as:

  • Active brake assist
  • Active blindspot assist
  • Active Park Assist
  • Collision prevention assist
  • Distronic Plus
  • Pre-safe with Neck- pro restraints
  • ESP dynamic cornering assist

Active bonnet assist and traffic sign assists are available as an optional extra, customers can choose the time of purchasing the car.

Other articles about Mercedes Benz you may be interested in

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How much does the C 250 cost?


The C 300d offers good power and superior engine torque thanks to the diesel engine. The OM654 is also very smooth and overall NVH levels are similar to that of a petrol engine. No major reliability issues were reported since the launch in 2019 which makes the C 300d a very popular model in the C class.