5 Most Reliable Mercedes Engines That Will Clock 1,000,000 Miles

In our analysis the most reliable Mercedes engines are; the OM617, M111, OM603, OM606, OM648, and the OM651 engine.

Since the introduction of the first Mercedes, the W02, in 1926, Mercedes as a brand has grown to firmly position all models bearing the 3-star badge as dependable and luxurious vehicles.

We won’t delve too deeply into history in this list of best Mercedes engines. Our focus will be on engines under the hood of vehicles that can be used on a daily basis as we determine if Mercedes engines are indeed reliable.

We’ll go back in time to the W100 era, starting in 1963, and pick out a couple of gems produced until the early 2000s.

We’ll take a deep dive into each rig and find out why they are solid power plants.

Let’s get into it..

Most reliable Mercedes engines - OM617

The Mercedes OM617 engine is a five-cylinder motor with a displacement of 3.0 liters and a turbocharger. The engine’s toughness is enhanced by a cast iron block and an aluminum head. It also counts as one of the most reliable engines ever built.

When it comes to performance, the OM617 is no slouch, producing 125 horsepower and 184 lb-ft of torque, which is more than enough for most applications. The turbocharger increases the engine’s power and overall performance.

Mercedes also used one of the best camshafts ever used in an internal combustion engine. The engine’s camshaft is extremely durable, and the crankshaft is forged, allowing it to withstand the high levels of stress associated with a diesel engine.

In this engine, a indirect injection system that is mechanical for durability is used for fuel efficiency. Furthermore, the fuel system’s inline fuel pump ensures that fuel is distributed evenly to each cylinder, improving performance and reducing engine wear.

This was a well-designed and built motor for an engine that sold 2.7 million units. What better way to confirm the OM617’s reliability than with a reference to the taxis that have famously clocked more than 500,000 miles, with one special 300D doing close to 3 million miles in Europe.

The OM617 is a simple motor that is easy to maintain and repair. A novice driver can easily run this engine with basic maintenance such as oil changes, air filter replacement, and fuel filter replacement.

The OM617 was first manufactured in 1974. The most memorable Mercedes paired with this motor is the 300D W123. This is without a doubt the best Mercedes engine.

OM617 reliability

oM617 in the Mercedes W123 - 300D

The build quality of the Mercedes Engine OM617 is one of the factors that contribute to its dependability. As previously stated, the engine has a cast iron block and an aluminum head, which makes it extremely durable.

The ease of maintenance is another important factor that contributes to the engine’s reliability. The OM617 is a simple yet robust engine, which means it can withstand beyond normal wear and tear, reducing the need for frequent repairs.

Between the naturally-aspirated 4-cylinder engine OM 616 – the predecessor of the OM617 – and this straight-5 diesel engine, the reliability goes to the diesel powerplant.

The motor was so good that almost 48 years later, the 300D W123 is still changing ownership in great condition.

All you need to do to keep it running smoothly is replace the timing chain if not already done, and also do the same for the fuel pump. The rest is bliss.

Most reliable Mercedes engines - M111

M111 engine in the W124 - 300E

The Mercedes M111 engine debuted in 1992 and was manufactured until 2003. It’s a four-cylinder engine that’s been on the market since the early 1990s.

The engine has a well-deserved reputation for durability and longevity, making it a favorite among high-mileage vehicle owners.

The aluminum block of the M111 engine reduces weight and improves fuel efficiency.

The engine also includes a balance shaft, which reduces vibrations and improves smoothness, making for a more comfortable driving experience.

The M111 engine introduced variable valve timing (VVT) on both the intake and exhaust camshafts. This technology aided in the enhancement of engine performance and fuel efficiency.

The engine also employs a sequential fuel injection system, which precisely controls the amount of fuel injected into each cylinder for maximum performance and efficiency.

One interesting fact about the M111 engine is that it was originally designed as a joint project between Mercedes and Mitsubishi.

The engine was used in several Mitsubishi vehicles as well as a few Mercedes models. This collaboration between two automakers with opposing design ideologies aided in the development of an engine that combined the best features of both companies.

The M111 engine was also the first in a Mercedes-Benz vehicle to feature electronic throttle control (ETC).

This technology enabled precise throttle control over the engine, resulting in smoother and more responsive acceleration.

M111 engine reliability

Over the years, the M111 engine has proven to be a reliable engine. With proper maintenance, this engine should last for many years and miles. However, there are a few common issues that M111 engine owners have reported.

The M111 engine has a history of head gasket failures. While this is a relatively uncommon occurrence, it can be costly to repair and may necessitate engine disassembly. Head gasket failure can be avoided with regular inspections and maintenance.

Failure of the timing chain tensioner is a constant issue with the M111 engine. The tensioner may eventually wear down and stop working, allowing the timing chain to become loose and possibly seriously harming the engine.

To avoid this, it’s crucial to have the timing chain tensioner inspected and replaced as necessary.

Yet, since both problems are avoidable and do not affect all engines, the credibility of the engine is not compromised.

Most reliable Mercedes engines - OM603

OM603 in the W463 G Class

The OM603 engine from Mercedes-Benz is a monster! It ranks as one of the most liked engines among Mercedes fans due to its remarkable dependability, toughness, and fuel efficiency.

The OM603 engine, if you’re not familiar with it, is a 3.0-liter inline-six diesel engine that Mercedes-Benz built from 1985 to 1993.

Several Mercedes-Benz vehicles, including the W124, W126, and W140 series, were equipped with it.

The OM603 engine’s design is among its most intriguing features. Because the engine block is built of cast iron, it is incredibly robust and resistant to damage.

It greatly contributes to the engine’s reliability and to the fact that it is still in use today.

In addition, the engine has a single overhead camshaft (SOHC) design, which has fewer moving parts and lowers the risk of mechanical failure. For DIY enthusiasts, this design makes the engine less complicated and simpler to maintain.

The maximum power output for the OM603 engine is 148 horsepower at 4,400 revolutions per minute, and the maximum torque production is 224 lb-ft at 2,400 revs per minute.

By today’s standards, these numbers might not seem all that spectacular, but it’s crucial to keep in mind that the engine was created in the 1980s and early 1990s, a time when fuel efficiency was a major concern.

Despite its low power output, the OM603 engine is known for its smooth and refined operation. The engine is also extremely fuel-efficient, thanks to its diesel fuel injection system, which helps to improve engine efficiency and reduce fuel consumption.

If repairs are required, the OM603 engine is relatively simple to service. Because of the engine’s simple design and construction, many repairs can be performed by a skilled DIY mechanic.

However, for more complex repairs or major overhauls, it is recommended that the engine be serviced by a professional mechanic who is familiar with Mercedes – Benz engines.

Vehicles using the Mercedes OM603 engine

From the mid-1980s to the mid-1990s, the Mercedes OM603 engine was used in a variety of Mercedes-Benz vehicles. The W124 E-Class, W126 S-Class, and G-Class SUV are among the most notable models.

The OM603 was available in both sedan and wagon variants in the W124 E-Class, providing a balance of performance and practicality.

The engine was offered in both naturally aspirated and turbocharged configurations, with output ranging from 148 to 177 horsepower.

The OM603 engine was also used in the W126 S-Class, providing ample power and luxury for Mercedes-flagship Benz’s sedan.

The engine was offered in both naturally aspirated and turbocharged configurations, with output ranging from 148 to 177 horsepower.

The G-Class SUV, also known as the G-Wagen, is perhaps the most iconic vehicle to use the OM603 engine.

The G-Class has been in production since the late 1970s and is a tough and capable off-road vehicle. From 1985 to 1991, the OM603 engine powered the G-Class, providing dependable and efficient power for this legendary SUV.

The OM603 engine was also used in Mercedes-Benz vehicles such as the W463 G-Class, W210 E-Class, and W140 S-Class.

Despite the fact that the engine was eventually replaced by newer designs, the OM603 is still a popular choice among Mercedes enthusiasts and collectors due to its dependability, durability, and fuel efficiency.

Most reliable Mercedes engines - OM606

OM606 engine in the W210

As a close cousin to the OM603, this engine packed a punch in terms of torque and was equally reliable. 500 hp from a turbo-charged OM 606 is not an overstretch. This Mercedes-Benz 3.0 L inline-six cylinder, DOHC diesel engine with indirect injection was a faultless engine.

It was produced between 1993 and 2001. It took the place of the OM603 engine’s single overhead camshaft (SOHC).

Mercedes had a 2996cc displacement diesel engine that matched the 2JZ. The OM606 diesel engine, which has 24 valves and a dual overhead camshaft, is not your typical engine, you read that correctly.

This is a gem with no DPF issues, fewer plastics, and engine aesthetic bells and whistles. In comparison to the gasoline version, the engine is extremely dependable and powerful, with a power output that can easily exceed 500BHP.

OM606 engine reliability

The OM606 motor does not have many complex issues. The only issue you might anticipate is glow plug failure.

The 606’s 3.0 liter inline 6-cylinder engine renders it mechanically invincible. The OM606 engine was manufactured from 1993 to 2001 and was used in well-known vehicles such as the E-Class and S-Class. This engine was available in two configurations: 300D (136 horsepower) and 300TD (177 horsepower).

Vehicles using the Mercedes OM606 engine

The OM 606 motor was used in the Mercedes Benz W210 300D (1995 – 1997), W140 (1997-1998), and W124 300D (1993-1996). They are all inline 6-engines that are solid and durable.

Most reliable Mercedes engines - OM648

OM648 in the W211

The reliability of a straight 6 engine is well documented, and the OM 648 is one such engine. This is one of the best Mercedes diesel engines.

Features include a 3.2-liter displacement in a straight-six, 24-valve, cast iron block diesel engine from Mercedes. The engine has a variable nozzle turbocharger and common rail fuel injection.

The engine manages to produce amazing torque while maintaining excellent fuel efficiency at 27+ city MPG and 37+ highway MPG.

Only the restyled S-Class in the body of the W220 and the E-Class in the body of the W211 were equipped with the 3.2-liter 6-cylinder inline engine Mercedes OM648 that was built from 2002 to 2006. A modification with a power reduction to 177 hp was available in addition to the standard version with 204 hp.

The motor came in two variations: 648.960 in the S320CDI and 648.961 in the E320CDI and E280CDI.

OM648 engine reliability

The om648 reliability is fair on most levels. What should you expect?

Glow plugs are the first glitch you will encounter with these engines. It’s however challenging to remove glow plugs or injectors without stripping threads in the aluminum cylinder head. This is the most glaring problem in this engine found in 2005–2006 E320CDI vehicles.

The OM648 engines are susceptible to soot buildup in the EGR.

With the negatives out of the way, you are bound to have a great experience with the om648 engine. This can be considered the most reliable Mercedes of all time. You can read more about the most reliable Mercedes diesel engine via the link below.

Most reliable Mercedes engines - OM651

OM651 in the W212 E - cLASS

The OM651 engine is a marvel of engineering, combining power, efficiency, and reliability.

This inline-four diesel engine boasts a 2.1 liters displacement.

While the OM617 engine was popular in European taxis in the early 1990s, the OM651 is the current equivalent of the renowned OM617.

The OM651 engine, which was introduced in 2008 as the successor to the OM646 engine, represents a considerable development in diesel technology.

The increased fuel efficiency was the most notable aspect. To reduce fuel consumption while maintaining exceptional power and performance, Mercedes combined turbocharging, direct injection, and clever engine management technologies.

The OM651 engine is lightweight and compact, but its performance is unrivaled. The engine’s cast-iron block, aluminum cylinder head, and high-pressure common rail fuel injection system are all built of aluminum.

A variable geometry turbocharger aids in the delivery of raw torque in this engine.

OM651 engine reliability

Diesel engines are extremely reliable. In this scenario, we’re looking at long-term viability and a positive ownership experience.

The longevity of an OM651 engine is influenced by a number of factors, including maintenance, driving conditions, and usage patterns. An OM651 engine can easily exceed 400,000 miles with regular servicing and proper care.

Oil is a key component of an engine that contributes to engine longevity and, in certain situations, is the fundamental cause of most engine problems.

Mercedes devised an innovative lubrication system for the OM651 engine, which is critical to its reliability. The engine is outfitted with modern oil filtration technology, which ensures that the lubricating oil is clear of impurities that could damage the engine’s components.

DPFs are standard on the majority of modern diesel engines. The OM651 engine can have DPF problems, however, this only applies to vehicles that travel short distances. Taxis rarely have DPF issues because the technology clears out potentially dangerous soot on extended travels.

Overall, the OM651 engine is unquestionably reliable, making it one of the most reliable modern engines.

Vehicles using the Mercedes OM651 engine

The OM651 engine’s versatility allows it to be used in a wide range of Mercedes-Benz cars. It powers several vehicles, including the C-Class, E-Class, GLC, and GLE.

Still on the Most reliable Mercedes engines

The om648 reliability is fair on most levels. What should you expect?

The OM648 engines are susceptible to soot buildup in the EGR.

A few questions to address before we wrap up on the most reliable Mercedes engines.

Which Mercedes V8 engine is considered the most reliable?

The M156 takes the crown in this category. It is a powerful V8 powerplant. This engine debuted in 2006 and was used in a number of Mercedes models, including the C63 AMG, E63 AMG, and CLK63 AMG.

The M156 engine delivers great horsepower, and despite a few flaws such as lifters and weak mounts, it is a fantastic engine.

What year of the Mercedes E-Class is considered the most reliable?

The Mercedes E-Class has a reputation for delivering dependable performance and engineering.

However, it is difficult to single out one year as the most trustworthy because reliability varies depending on aspects such as model, engine, and individual vehicle maintenance and care. In this regard, let us establish a distinction between old and new.

In the old engines, there was a legendary motor in the W124 chassis that ran on the M111 engine. The M278 and M157 engines were used in the W212 generation (from 2009 to 2016). However, for the finest experience, we recommend the M111.

Wrapping up

The 3-star badge ticks all the boxes for a reliable and perfect engine and so do most of the motors under the 3-star hood. This list of the most reliable Mercedes engines highlights engines that will rarely fail or torment you in maintenance.

You can buy a car with any of these engines that has 500,000 miles on the odometer and still travel around the world.

That wraps up our analysis of the best Mercedes-Benz engine. Hope you can now pick the best engine from the 3-star family.

People keep wondering – Are Mercedes V8 engines reliable? The answer is in the article below – the best Mercedes AMG engines.