Mercedes M156: Everything You Need To Know

When you talk about high-performance engines, you cannot count out the AMG. AMG created some of the most influential and recognizable machines throughout the years, including SLS McLaren.

This has been further proven when they became the subsidiary of Mercedes when they continue to do cosmic stuff, and such is the birth of the famed naturally aspirated V8, the Mercedes-Benz M156.

Let us learn more about the engine’s design, applications, issues, reliability, potential, and many more.

What are Mercedes M156 Engines?

The Mercedes M156 engines were the last naturally aspirated engine that AMG ever made, and Mercedes entirely went to turbocharging after that. However, it is the first V8 automobile powerhouse that AMG and Mercedes worked on together – such a great collaboration, though.

It also became the engine used on multiple numbers of high-performance Mercedes AMG vehicles later.

The M156 engine is the successor of the famous M113 K. It displaces 6,208 cc and shares little to no features with the previous Mercedes-Benz-derived engine like the M155.

The M156 engine displacement, contrary to the 6.2 L, is marketed as a 6.3 Liter to commemorate Mercedes’ first production V8, the 6.3 Liter M100 engine.

The automaker’s expertise in racing technology, extensive automotive knowledge, and abundant resources reflected the block design, bore spacing, and other features to fit the AMG standards perfectly.

Let me pull a short story. Before Mercedes bought the majority of its shares, AMG started as an independent business that focused mainly on modifying and upgrading Mercedes vehicles into high-performance machines.

Later on, in 1999, Mercedes became the majority shareholder of the tuning company, and in 2005, the AMG became a wholly-owned subsidiary.

This time, the two began working the first engine that would be exclusively developed in the Affalterbach plant and would go on as the flagship powerplant for all AMG-badged cars.

Mercedes M156 was eventually replaced by the twin-turbocharged 4.0 Liter M176/M177/M178 and the 5.5 Liter M157 engine.

Engine Specifications and Design:

  • Production Run: 2006 – Present
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Aluminum
  • Configuration: V8
  • Bore: 102.2 mm
  • Stroke: 94.6 mm
  • Valvetrain: DOHC four valves per cylinder
  • Displacement: 6.2 L (6208 cc) badged as 6.3 L
  • Compression Ratio: 11.3
  • Weight: 452 lbs.
  • Maximum HP: 507 HP at 6,800 RPM
  • Maximum Torque: 465 lb-ft at 5,200 RPM

The Mercedes M156 engine is a naturally-aspirated, water-cooled, eight-cylinder gasoline engine. It has a cylinder bore diameter of 102.2 mm, a piston stroke of 94.6 mm, and an 11.3 compression rating.

Each cylinder bank is arranged in a ‘V’ configuration that features an aluminum head with four valves per cylinder and dual overhead camshafts. The engine has a total of 32 valves which were actuated using bucket-type followers, resulting in a tight and compact Valvetrain capable of higher power output.

The cylinder block is made from solid but lightweight aluminum material. It features a closed-deck design inspired by high-performance racing engines, the same concept they used on the SLR McLaren’s M155.

The M156 was the first mass-produced engine to use a wire-arc spray coating called Nanoslide on the cylinder walls. This equipped technology increased its durability and reduced friction by half, around 230-degrees Fahrenheit compared to traditional cast-iron cylinder liners.

The crankshaft of M156 is made from a forged steel alloy, and the connecting rods are also based on the concept found in modern racing engines.

The standard M156 versions came with a cast hypereutectic pistons, unlike the P31 who introduced new Mahle forged pistons linked to a lighter crankshaft by even connecting solid rods. These upgrades were continued and carried over to other 63 models.

Different from the naturally aspirated AMG M113 and its supercharged sibling M113K, M156 engines use only one spark plug per cylinder – contrary to the two. Furthermore, Mercedes also included a variable valve timing system for both the intake and exhaust valves, operated through an electro-hydraulic cam adjuster.

Launched in the 2007 CLK63 AMG, the M156 power output was rated at 475 HP at 6,800 RPM with 465 lb-ft of torque at 5,200 RPM. In the same year, CLS63 and E63 also feature M156, rated at 507 HP at 6,800 RPM with 465 lb-ft of torque at 5,200 RPM. The 2007 ML63 has 503 HP, the 2008 C63 has 451 HP, and the final C63 has 500 HP.

The engine was somehow uprated and buffed up the power output at 518 HP and 465 lb-ft of torque in the later S63, SL63, E63, CLS63, and CL63 models.

Applications of the Mercedes AMG M156 Engine:

  • 2006 – 2011 E 63 AMG
  • 2006 – 2011 ML 63 AMG
  • 2006 R 63 AMG
  • 2006 – 2011 S 63 AMG
  • 2006 – 2011 CL 63 AML
  • 2006 – 2010 CLK 63 AMG
  • 2006 – 2010 CLS 63 AMG
  • 2008 – 2015 C 63 AMG
  • 2008 – 2011 SL 63 AMG

Engine Tuning, Upgrades, and Modifications

Even without the tuning and upgrades, this engine is still a high-performance beast. With that kind of maximum power at 518 HP, it is easy to say that you can surpass the 550 HP mark with no sweat at all.

However, if you decided to go to more extensive production, you will need either replacement of headers or forced induction – basically two choices at your disposal.

Some steps or stages need to be done to fine-tune your M156 engine. The first stage is most likely the ECU reflashing, a change in the exhaust manifold, and camshafts.

You will need a fuel pump upgrade, high-flow fuel injectors, performance exhaust, and catalyst in the next stage. Add that with the forced-induction kit, ported and polished head, change the internals, and install larger valves.

In this way, you can gain at least 50-60 HP.

The last stage requires many upgrades and is quite expensive, but it is worth it since it can tap the elusive 1000 HP line.

You will need a 3.0 L twin-screw compressor module, 1000 HP liquid to air intercooler, high flow fuel rail system, high capacity fuel injectors, and molded silicone couplers.

Add that with an intercooler water recovery tank, 8-rib Direct drive belt system, cross-flow heat exchanger, intercooler water pump, power-steering reservoir relocation assembly, and Weistec Engineering Stage 3 Supercharger System ECU reflash.

Problems Surrounding the Mercedes M156 Engine:

The AMG M156 Legal Issues and Lawsuit

In 2011, a lawsuit was filed against the M156 engine. Mercedes and AMG found themselves in the court defending against the accusations pointed to them.

The lawsuit, as mentioned earlier, was filed in the United States in New Jersey District Court. The suit cites that the engine used in the 2007 to 2011 Mercedes AMG model cars, the M156, was defective, leading to the vehicles’ demise in premature wear and tear guise.

According to the complainant, the combination of both engine’s 9,310-grade steel valve lifters and cast nodular model were the culprits of the early engine deterioration. The plaintiffs handed the case over to the court because the issue pointed towards the alleged Mercedes and AMG were not addressed since 2007.

The lawsuit was lengthy and lasted more than a year, but in November 2012, the litigation was settled when the New Jersey District Court dismissed the case for lack of standing.

The plaintiff was given a chance to regroup and amend their initial suit to show that they have the right to sue. However, given such an opportunity, the plaintiffs made no further filings with the court, closing the case altogether. In January 2013, the court signed an order to complete the case.

Apart from the abovementioned issue of the M156, there are other common problems that you might face or encounter with the engine. 

First is the crankcase breather valve. There are two ways in how the breather valve fails. The most common is that the diaphragm on the valve deteriorates. The other way is that the hose from the crankcase going to the valves starts to become brittle and develops cracks.

This kind of issue worsens over time and may lead to increased oil burning, misfires, and excessive smoke from the tailpipe.

The next issue also affects large numbers of engines. Oil leaks affected M156 when its camshaft solenoid cover gaskets, valve cover gaskets, and oil filter housing gaskets start to fail. These are standard maintenance items, so they should be replaced periodically.

If oil leaks remain unattended, this can damage peripheral components like the drive belt pulleys, alternator, air conditioning compressor, drive belt, and transmission cooling hoses.

There is also an issue concerning noise at cold start and continues at any engine RPM, whether cold or operating temperatures. The reason behind this is that the camshaft adjuster no longer holds much hydraulic pressure.

This is observed mainly on engine startup.

Drive belt pulleys of the AMG 156 engine is a plastic-made design with a pressed on bearing. Pulley failure in the engine can damage the drive belt, and when that happens, the belt can also damage the coolant breather port on the thermostat.

Mercedes-Benz AMG M156 engine-equipped vehicles up to 2012 have cylinder head bolts that have the tendency to break, allowing the coolant to infiltrate the combustion chamber. That is why it is recommended to update the older design bolts with new ones.

The intake manifold also has some troubles since it houses the engine’s twin throttle bodies. That center mounting plate starts to deteriorate over time, causing rough idling in some instances.

Other M156 issues that need to be addressed are the camshaft and Hydraulic Lifters. These components should be considered regular maintenance items because they show their wear around 100,000 miles.

The wear happens on the left and right intake camshafts, and if not resolved, the cam lobe will eat through the hydraulic lifter. Also, engines with high mileage should have the oil checked or valve covers for any signs of wear.


The Mercedes-Benz AMG M156 is, for the most part, reliable and durable. The engine revs freely, has a really nice torque curve, lots of power, and potential. The energy it produces can compete at the highest level and can floor most of its competitors.

AMG M156 engine’s attributes can be considered as one of the best at that time given the expertise and knowledge of the AMG and Mercedes in racing development. They equipped this to make the engine much crazier and turn the 63 series to go berserk.

Even though it has a fair share of troubles – which can be solved and are mainly minor, it somehow outweighs the cons.

I hope that this simple explanation about the Mercedes M156 engine helped you cleared some questions regarding the engine’s design, application, reliability, issues, and overall impact on the automotive industry.

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