|Mercedes-Benz M156 engine|
|Configuration||Naturally aspirated 90° V8|
|Displacement||6.2 L; 378.8 cu in (6,208 cc)|
|Cylinder bore||102.2 mm (4.02 in)|
|Piston stroke||94.6 mm (3.72 in)|
|Valvetrain||DOHC 4 valves x cyl.|
|Fuel system||Fuel injection|
|Oil system||Wet sump|
|Power output||451–622 hp (457–631 PS; 336–464 kW)|
|Torque output||630–650 N⋅m (465–479 lb⋅ft)|
|Predecessor||Mercedes-Benz M113 engine|
|Successor||Mercedes-Benz M157 engine|
The M156 is the first automobile V8 engine designed autonomously by Mercedes-Benz subsidiary Mercedes-AMG, as previous AMG engines have always been based on original Mercedes engines. The engine was designed to be a naturally aspirated racing unit, and is also used in a number of high-performance AMG-badged Mercedes-Benz models.
The M156 displaces 6,208 cc (6.2 L; 378.8 cu in) and shares very little with other Mercedes-Benz engine families like the M155. The bore spacing, block design, and other features are unique to the AMG engine.
Although this engine displaces 6.2 litres, it is marketed as the "6.3" to commemorate Mercedes' famed 6.3 L M100 engine, its first production V8.
The engine uses a bore and stroke of 102.2 mm × 94.6 mm (4.02 in × 3.72 in). When introduced in the 2007 CLK63 AMG, output was 475 hp (482 PS; 354 kW) at 6,800 rpm with 630 N⋅m (465 lb⋅ft) of torque at 5,200 rpm. For the 2007 CLS63 and E63, output was 507 hp (514 PS; 378 kW) at 6,800 rpm with 630 N⋅m (465 lb⋅ft) of torque at 5,200 rpm. The 2007 ML63 had 503 hp (510 PS; 375 kW), and the 2008 C63 had 451 hp (457 PS; 336 kW). The final 2015 C63 had 500 hp (507 PS; 373 kW).
The engine, however, has been uprated to produce 518 hp (525 PS; 386 kW) and 465 lb⋅ft (630 N⋅m) of torque in the late S 63, E 63, SL 63, CLS 63 & CL 63 models.
In 2011, a class action lawsuit was filed in United States District Court in New Jersey against Daimler AG, Mercedes-Benz, Mercedes-AMG for alleged defects in the M156 engine contained in AMG vehicles built in 2007–2011 model years leading to premature wear. The plaintiff claimed the combination of cast nodular iron camshafts and 9310 grade steel valve lifters contributed to the premature wear, but the defendants had known about the defect since 2007.
The lawsuit lasted approximately 14-months. In November, 2012, litigation came to a halt when the New Jersey District Court dismissed the plaintiffs’ first amended complaint for lack of standing. The plaintiffs were given the opportunity to further amend their complaint to show that they had standing to sue, but plaintiffs made no further filings with the Court. On January 7, 2013, the Court signed an order closing the case. 
The M159 is a version used in Mercedes-Benz SLS AMG and current AMG GT3 racecar. Compared to the standard AMG engine, the SLS's engine includes an all-new intake system, reworked valvetrain and camshafts, the use of flow-optimised tubular steel headers and dethrottling of the exhaust system. The engine also utilizes a dry-sump lubrication system to lower the center of gravity of the car.
|Engine code||Years||Power output||Torque||Redline|
|M 159||2010-2012||571 PS (420 kW; 563 hp) at 6,800 rpm||650 N⋅m (479 lb⋅ft) at 4,750 rpm||7,200 rpm|
|M 159||2013-2015||591 PS (435 kW; 583 hp) at 6,800 rpm||650 N⋅m (479 lb⋅ft) at 4,750 rpm||7,200 rpm?|
|M 159||2013-2014||631 PS (464 kW; 622 hp) at 7,400 rpm||635 N⋅m (468 lb⋅ft) at 5,000 rpm||8,000 rpm|
- Class action lawsuit to be filed against Mercedes alleges AMG V8 defects
- Regar, Jacob. "Update: Mercedes Benz AMG Class Action for the M156 V8 Engine". jacobregarlaw.com/Blog. Jacob Regar Law. Retrieved 16 February 2013.
- Mercedes-Benz SLS AMG: fascination and high tech: The new 'Gullwing' from Mercedes-Benz
- "New AMG 6.3 Liter V8 Engine -In Detail". GermanCarFans. Retrieved January 16, 2006.