Is the  Mercedes C300 a reliable car?

This blog will list the various reasons that make the Mercedes Benz C 300 a reliable car. We also take a closer look at each of the reasons for the reliability of the C 300.

 Is the  Mercedes C300 a reliable car?

Yes, the Mercedes Benz C 300 is a reliable car because of the following reasons:

  • Latest Engine
  • (ISG) integrated starter generator
  • Latest transmission
  • MRA-II platform
  • Onboard electrical systems

All the reasons for the great reliability of the Mercedes Benz C 300 are explained below:

Latest engine 

The Mercedes Benz C 300 is powered by the M254 20 DEH LA, it is a newly developed petrol engine based on the bigger inline 6 cylinder M256 engine. Mercedes Benz has discontinued the M274 petrol in all of its models and currently uses the M254 engine.

The power output of the M254 in the Mercedes Benz C 300 is 254 horsepower and 400 NM of torque. The torque curve of the engine is very flat, maximum torque is generated at 2000 RPM and it lasts until 3500 RPM.

The M254 has a complete aluminium build; the pistons are forged and lightweight to keep the unsprung mass to a minimum level. The crankshaft is balanced by two balancer shafts and the lower section of the oil pan is made out of durable plastic. 

There is no engine oil dipstick and the engine oil is calculated by an electrical level sensor. Drivers can check the engine oil by setting the workshop menu in the instrument cluster.

The M254 has very reliable piezo-direct fuel injectors; the fuel injectors are directly installed in the fuel rail. Petrol is stored in the fuel rail under high pressure. The high pressure is developed by the high-pressure fuel pump with a quality control valve.

The M254 has a wastegate turbocharger along with an electric air compressor. The air compressor is connected to the 48 V electrical system. It generates boost pressure at low engine speeds. Since the compressor is electric, it does not require any power from the engine or exhaust gases to generate boost pressure.

Once the engine speed is high, the wastegate turbocharger can take over the task of supplying charged air to the intake manifold. The charge air intercooler is liquid-cooled with its dedicated secondary coolant circuit.

Under partial load conditions, both the turbocharger and the air compressor can work together to generate the required amount of boost pressure.

Integrated starter Generator 

The M254 has an integrated starter generator or ISG. the ISG has greatly improved the reliability of the C 300. It is the first time the C Class is equipped with an ISG; the electric motor is housed just before the torque converter.

It is capable of driving the engine and generates an additional 22 horsepower. When the electric motor is not supplying drive to the engine, it can act as a power generator. The power generated by the electric motor is stored in a 48 V high voltage battery.

The M254 is a completely beltless engine, all the ancillary components like the air conditioning compressor, alternator and coolant water pump are electric. The 48 V onboard electrical battery supplies power to the ancillary components. 

Mercedes Benz has labelled this technology as EQ Boost and it is more reliable than the belt-driven starter generator found in the previous generation model with the M260 engine.

Latest Transmission

The Mercedes Benz C 300 has the latest 9 g Tronic automatic transmission. It consists of 4 sets of planetary gears and the gear shifts are very smooth. The electrohydraulic valve body has an integrated transmission control unit. Both of them are housed inside the transmission and fully submerged in the automatic transmission fluid.

The Oil pan is specially designed with inbuilt ATF oil filters, minute metal particles are collected in the filters so that the valve body remains clean and there are no breakdowns due to blockage in the solenoids. 

All the gears are actuated by individual solenoids, therefore the 9 G Tronic transmission can not only make multiple gear changes but also skip certain gears according to the engine load and input torque available.

The automatic transmission fluid is replaced after 4 years or 60,000 km. This preventive maintenance helps with the reliability of the C 300. The transmission is not sealed from life, when the ATF is renewed the oil pan is also replaced as the oil filters cannot be replaced separately. 

MRA-II platform

The Mercedes Benz C 300 is based on the second iteration of modular rear architecture. Mercedes Benz introduced the MRA II platform with the new generation S Class. The C 300 is also styled after the S Class. 

The MRA II platform provided more legroom in the back despite having rear-wheel steering with a 2.5-degree steering angle. The rear wheels can turn independently of the front wheels based on the vehicle’s speed. 

The turning radius of the C Class is also reduced by 0.4 M compared to the previous generation. The MRA-II platform is more rigid without any significant increase in the overall weight of the body shell. 

There are independent McPherson struts on the front and a separate coil and spring suspension setup at the rear axle.

Anti-roll bars connected to the link rods are present on the front and rear sides in order to minimise the body roll. The front tyre size is 255/45 R18 and 205/55 R17 on the rear axle due to the rear-wheel steering.

Onboard electrical systems

The Mercedes Benz C 300 has a completely reworked onboard electrical system. There is a 48 V high voltage battery that is connected to the integrated starter generator. A DC to DC convertor is used to charge the onboard 12 V battery.

Battery voltage monitoring systems continuously check the voltage of the onboard 12 V battery. If there is a risk of discharging the 12 V battery, then the battery disconnect switch is opened by the front signal actuation and acquisition control unit. 

Opening the battery disconnect switch prevents the main battery from getting completely discharged and the integrated starter generator is capable of starting the engine with power from a 48 V battery. There is no need for a conventional starter motor

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This blog explained the various factors that are responsible for the reliability of the C 300. Mercedes Benz also gives 3 years unlimited KM standard warranty to the C 300. There is also the choice to purchase an extended warranty package from the fourth to the sixth year. An extended warranty can help to reduce the maintenance cost by covering the cost of any unexpected repairs that may occur.