What is the difference between Mercedes Benz SL and Mercedes Benz SLK?

This article will answer the following questions: what is the difference between Mercedes Benz SL and Mercedes Benz SLK? What are the engine options available in Mercedes Benz SL and SLK? Which one is more reliable?

What is the difference between Mercedes Benz SL and Mercedes Benz SLK?

The key difference between the Mercedes Benz SL and SLK are listed in the table below:

The Mercedes Benz SL and Mercedes Benz SLK are two-door convertible sports cars but they are based on completely different platforms. 

The Mercedes Benz SLK, on the other hand, was a fairly new model it was launched in 1996 and the design was originally inspired by the original SL roadster from the 1950s however it was a much lighter and smaller car than the SL.

The SL stands for sport and lightweight while the k represents a shorter version of the SL. Mercedes Benz only developed three generations of SLK class; the 3rd generation launch in 2011 was the final generation and the production was discontinued in 2020. The SLK was replaced by the SLC model which was the best on the same platform but featured the latest Mercedes Benz design language and brand new turbocharged engine.

Mercedes Benz SL was also more technologically advanced than the SLK model. It had an advanced active body control suspension system compared to the standard mechanical suspension setup on the SLK. Both the SL and SLK models also had high-performance AMG versions but the SL had a V8 engine with a supercharger while the SLK only got a naturally aspirated engine.

The Mercedes Benz SLK was popular in the international markets as it was cheaper compared to the bigger SL model. The Vario roof convertible system in the SLK was very reliable as it was lighter and smaller compared to the SL.

The Mercedes Benz SLK was the first model with magic sky control. The panoramic glass on the roof can become completely dark at the touch of a button. The magic sky control significantly reduces the temperature inside the cabin and also reduces the load on the air conditioning system of the vehicle. 

Considering the popularity of the magic sky control feature Mercedes Benz later introduced it in the SL model as well. 

The Mercedes Benz SL and SLK are two-door roadster models so even in the international market they were available in limited numbers. The high-performance versions were not even sold in developing markets like China and India.

 After the 6th generation, Mercedes Benz halted the production of the SL class in 2020. Only the Mercedes Benz SLC roadster was available other than the AMG GT roadster. 

What are the engine options available in the Mercedes Benz SL and SLK?

The Mercedes Benz SL only came with V6 and V8 petrol engines. Since SLK was a shorter and lighter version of the SL it was available in inline 4 cylinders,  V6  and V8 engines. The m276 V6 engine was common in both Mercedes Benz SL and SLK. M278 was exclusively available in SL. The SLK 55 AMG was the only SLK with a V8 engine.

The power available in the SLK was from 180 horsepower up to 415 horsepower, SL on the other hand had a horsepower range of 300 to 600 horsepower. The latest generation of the SL is exclusively an AMG model. It is available in 3 variants: the SL 43, SL 55 and SL63. 

The SL55 and SL63 are 4matic models, SLK was strictly a front-engine rear-wheel-drive car. The SLC which is the successor of SLK is also available only in rear-wheel drive.

The M276 in the SLK and SLC is of the same 3.0-litre displacement but the SLC had turbochargers instead of a naturally aspirated M276 engine. 

The boost pressure is controlled by electro-pneumatic transducers that can control the wastegate linkage connected to a vacuum cell. The boost pressure transducers are controlled by the signal from the engine control unit.

The Mercedes Benz SL used only 7G and 9G Tronic automatic transmission while the SLK had6-speed manual and 7-speed automatic transmission options. The manual transition became popular among car enthusiasts as the SLK was the only model in the Mercedes Benz lineup with a manual transmission option.

The SLK roadster was even available in a diesel engine variant in the European market. The diesel engine in the SLK was bi turbocharged inline 4 cylinder OM651 that produced 200 horsepower and 500 Nm of torque.  Both the turbochargers were wastegate type however one turbo was low stage while the other turbo activated only at the higher engine speeds.

OM651 was also the first diesel engine with Mercedes Benz Nanoslide.  Nanoslide 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.

Which is more reliable: Mercedes Benz SL or the SLK?

The V6 and the V8 petrol engine in the Mercedes Benz SL and SLK were very reliable but few models suffered from late cranking issues due to fault camshaft adjustment. All the engines have camshaft adjustments for both intake and exhaust camshafts which can advance or retard the opening and closing of intake as well as exhaust valves. 

The camshaft adjusters have spring-loaded chambers that can change the angle of the camshaft to the crankshaft by 40 degrees. The engine oil is filled into the chamber and the electrical actuator controls the flow of the engine oil into the camshaft adjusters.

A faulty adjuster cannot lock the basic position of the camshafts and the engine takes a long crank to determine the ignition angle. Replacing the camshaft adjuster can be an expensive job but after replacement, the fault does not occur.

Apart from long cranking issues, older Mercedes Benz SL models suffered from hydraulics leaks in the Vario roof cylinders. The Vario roof system used many small hydraulic cylinders to fold the hardtop into the trunk. The Vario roof in the SLK used a combination of electric motors and hydraulic cylinders to fold and unfold the convertible roof. 

The sixth generation of the SL and the third generation of the SLK had no major similar reliability but the customers preferred the SLK as it was cheaper to maintain due to its simple construction and conventional suspension systems.

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Conclusion

The Mercedes Benz SL and SLK were very popular convertible roadsters, SL offered a more luxurious experience thanks to more space in the interior while the SLK offered similar performance and better handling as it was very light compared to the SL. The SLK was also very cheap and many customers liked the inline 4-cylinder engine with the manual transmission models.