techXXX
Evolution of the Mercedes Petrol V8
In this blog, I go over the evolution of eight Mercedes V8s over seven generations in terms of their construction, performance, reliability, and applications. In the end, I will rank them into three tiers.
Mercedes-Benz is the non-American automaker most closely associated with petrol V8 engines. Today, I go over the evolution of eight Mercedes V8s over seven generations in terms of their construction, performance, reliability, and applications. In the end, I will rank them into three tiers.
M100
- 1963-1981
- 6.3L / 6.8L
- SOHC, NA, Mechanical fuel injection
- Cast iron block + Aluminum head, closed deck, semi dry sump (6.8L)
- 600, 300SEL 6.3, 450SEL 6.9
The M100 was Mercedes’ first V8, originally designed to power the W100 600. It has a cast iron block with fully forged internals and aluminum heads in a SOHC layout. The M100 uses mechanical fuel injection, initially of Mercedes’ proprietary design. With the introduction of the W116, the 6.8L adopted Bosch Jetronic. The 6.8L also features a semi-dry sump lubrication system, only to fit inside the engine compartment of the W116. All M100s were hand-built and meticulously tested.
Arguably the most robust, best engineered, and best built European V8 of all time, the M100 delivered satisfactory performance for the time. It made up for the lack of performance, like that of the carbureted Maserati V8, with exceptional longevity. The M100 also has the honor of being exclusive to three of the most collectible and iconic Mercedes vehicles, all of which I have covered in an earlier blog.
M116 / M117
- 1969-1991
- M116: 3.5L / 3.8L / 4.2L
- M117: 4.5L / 5.0L / 5.5L
- SOHC, NA, Mechanical fuel injection
- Cast iron block (-1978), Alusil (1978+), closed deck
- 350, 380, 420, 450, 500, 560
The M116 was Mercedes’ first mass-produced V8. Initially, it had a cast iron block like the M100; this was replaced by an all-aluminum, Alusil block in 1978. Like the M100, the M116 uses a SOHC design with Bosch Jetronic mechanical fuel injection. The M117 is essentially the same engine but with a larger block.
The M116 and M117 delivered competitive performance for the time, especially the late 5.5L M117 found in the 560 models. These engines are now recognized as long-lasting powerplants found in some of the best built European classics. One challenging area is with the mechanical fuel injection system, which very few know well today.
M119
- 1989-1999
- 4.2L / 5.0L / 6.0L (AMG)
- DOHC, NA
- Alusil, open deck
- 420, 500, 60 AMG
The M119 was Mercedes’ first DOHC V8. This setup improved engine breathing, resulting in small performance gain over the M117, despite a reduction in displacement. The M119 also adopted an open-deck crankcase design and electronic fuel injection. It also features variable valve timing on the intake cams. Thanks to these updates, the M119 is a great, reliable daily driver even till this day. AMG made a 6.0L version, though it is less iconic than the original modified DOHC M117 today.
M113 / M155
- 1997-2011
- 4.3L / 5.0L / 5.4L
- SOHC, NA or supercharged
- Silitec (Lokasil) except M155, open deck, magnesium intake manifold, magnesium valve covers
- 430, 500, 55 AMG, SLR McLaren
The M113 was an exercise in cost-cutting and modern manufacturing. It is considerably lighter than the M119 and was much cheaper to produce. Notably, the M113 returned to SOHC design but retained the open-deck crankcase. It also moved to the Silitec process, which is comparable to Lokasil and is cheaper than the Alusil process. I have detailed them in a previous article. Other features include magnesium intake manifold and valve covers. The AMG-specific 5.4L supercharged variant, colloquially referred to as M113K, adds forged crankshaft and reinforced crank journals, while the M155 found in the SLR McLaren further features forged aluminum pistons.
The M113 delivers satisfactory performance despite SOHC design, thanks to three valves per cylinder. Notably, it reaches peak torque much quicker than the M119. The supercharged 5.4L variants are still loved by enthusiasts today, with the SLR McLaren being one of the last well-built and collectible Mercedes vehicles. Both are rising in value.
M273
- 2005-2013
- 4.7L / 5.5L
- DOHC, NA
- Silitec (Lokasil), open deck
- 450, 500/550
The M273 is more like the successor to the M119 than that of the M113, as it brings back DOHC heads, single spark ignition, and variable valve timing. Still, the M273 keeps the Silitec crankcase with magnesium intake manifold. VVT became continuously adjustable and is found on both the intake and the exhaust cams. Mercedes also introduced a new electronic thermostat.
Thanks to DOHC layout and VVT, the M273 breathes much better than the M113 and is considerably more powerful. However, it is less fuel efficient and less reliable. Early units suffered from the infamous idler gear problem, while its timing chain guide and camshaft adjusters are not the most robust, either.
M156 / M159
- 2006-2014
- 6.2L
- DOHC, NA
- Aluminum, NANOSLIDE, closed deck, magnesium intake manifold, dry sump (M159)
- 63 AMG, SLS AMG
The M156 is the only engine designed fully by AMG. Unlike its contemporaries, the M156 uses the NANOSLIDE spray-on iron cylinder liner, the first engine manufactured with this process. It has a unique magnesium intake manifold with twin internal throttle bodies. The tube for wires going to these throttle bodies is a common point of magnesium corrosion and air leak. The M159 is the upgraded variant with forged crankshaft and forged pistons, dry sump lubrication, and revised valvetrain.
Thanks to its generous displacement, the M156 is widely loved. Its linear power delivery and high peak output make it the ultimate naturally aspirated V8. However, the M156 has a few failure points: Besides the intake manifold corrosion issue, the M156 is known to suffer from common camshaft and lifter wear as well as camshaft adjuster wear problems. All but late production units also suffer from weak head bolt design. The M159 in the SLS AMG is the ultimate variant with most of these issues addressed from the get-go.
M278 / M157
- 2010-2020
- 4.7L / 5.5L
- DOHC, biturbo, DI
- Silitec (Lokasil) except 2016+ M278 (NANOSLIDE), open deck
- 500/550, 63 AMG
The M278 was Mercedes’ first turbocharged and direct-injected V8. It shares essentially the same engine block with the M273, therein lies its main weakness. The M278 uses piezoelectric fuel injectors. Mercedes also added an electronically controlled oil pump to reduce oil pressure when possible. The M157 is just the 5.5L version with a forged crankshaft. Mid-way through its production cycle, the M278 adopted NANOSLIDE cylinder lining in 2015, this update addressed its bore scoring issue; the M157 did not receive this update, as AMG was already moving away from this architecture.
The M278 and M157 are torque monsters, delivering more low-end power than their predecessors and successors alike. For this reason, despite their horrendous reliability records, many enthusiasts still love them, although these engines were only put in heavy and somewhat boring cars.
M176 / M177 / M178
- 2014-
- 4.0L
- DOHC, biturbo (hot), DI
- Aluminum, NANOSLIDE, closed deck, dry sump (M178)
- 500/550, 560, 580, 63 AMG, AMG GT, Aston Martins
The M176 was a blank sheet design with turbocharging in mind. It seemingly learned lessons from BMW’s disastrous N63 introduced half a decade earlier, though it is unclear whether these were the right lessons. Like the M278, the M176 still uses piezoelectric fuel injectors. It also features twin-scroll turbochargers. From 2019, mild hybrid was introduced. The M177 is an AMG-built variant with a forged crankshaft, while the M178 adds forged pistons.
Arguably, the M176 was a step backwards with smaller displacement and lower torque. Still, with a stronger crankcase and higher boost, it can deliver thrilling top-end power. However, the M176 and its AMG brethren are maddeningly complex and difficult to fix. It is the first Mercedes V8 to use single-roll timing chains with bottom-mount oil filter, just like a BMW.
Ranking
Tier 1: M100, M113K, M155, M156/9
Tier 2: M116/7, M119, M113, M273
Tier 3: M278, M157, M176/7/8
Tier 2: M116/7, M119, M113, M273
Tier 3: M278, M157, M176/7/8
