Best diesel Mercedes engines

Best diesel Mercedes engines

Although most diesel engines have a solid reputation, not all of them are created equal. Some are excellent power plants, while others are simply – trouble. The article on Mercedes diesels to avoid (link below) explains the bad engines.  But we won’t delve into the troublesome engines in this article – we’ll cover the best diesel Mercedes engines.

Mercedes-Benz has a reputation for producing some of the most reliable and durable diesel engines. These engines have proven their worth time and again. Powering some of the most iconic Mercedes-Benz models in history, from compact cars to luxury SUVs. 

As we take a deep dive into the most reliable mercedes diesel engine engines, we’ll go over their key features. We’ll also look at performance capabilities, applications, and why they’re considered among the best in the industry.

We begin with an engine billed as the most reliable Mercedes engine…


Best diesel Mercedes engines - OM617 engine

Best diesel Mercedes engines - OM617 engine

First introduced in 1970, this engine was under the hood of multiple Mercedes models released after that year.

One of the best diesel Mercedes engines. The OM617 motor powered the 300D Mercedes – a legendary vehicle that stood the test of time and proved to be reliable to a fault.

The 300D gained a monicker – the taxi Mercedes. To date, there are a couple of 300D Mercedes operating as taxis in Europe with unbelievable figures on the odometer.

Despite Mercedes releasing variants of the OM617 engine including a turbocharged version in 1976, the naturally aspirated original version was the winner on reliability.  One of the most reliable engines built in the 21st Century. So, let’s go deeper and discover the magic of the OM617 engine.

Notable Features Of The OM617 engine

The cast iron cylinder block and aluminum cylinder head design were distinguishing features of the OM 617 engine. The cast iron block increased longevity and heat dissipation. To reduce maintenance costs, the engine also included a camshaft powered by a chain.

Other key features included:

  • Straight 5 cylinders
  • 3000 cc displacement
  • A double-row chain timing drive
  • A chain-driven valvetrain
  • 2 valves per cylinder to make 10-valve
  • Single Overhead Camshaft

OM617 engine reliability

The OM617 has indeed earned its place as one of the best diesel Mercedes engines.  The use of a cast iron block is one of the key factors that improved the OM617 engine’s reliability. Cast iron is a tough and long-lasting material that can withstand high temperatures and pressure without warping or cracking, ensuring that the engine stays in good working order over time.

Another element that contributes to its durability is its sturdy timing chain. Instead of timing belts, timing chains make an engine last longer and require less maintenance.

The OM617 engine also features a straightforward and effective fuel injection system that raises fuel efficiency and reduces emissions. By design, this reduces fuel costs and keeps engines within the boundaries of energy laws.

Let’s highlight more features that reinforce the OM617’s reliability….

Simple design: The OM617 engine has a simple design with fewer moving parts, which reduces the possibility of mechanical failure.

Low-pressure fuel injection: The engine uses low-pressure fuel injection, which aids in preserving the structural strength of its internal components.

Durable components: Many of the OM617 engine’s components, such as the pistons, connecting rods, and crankshaft, are made of high-quality materials that are designed to withstand daily use.

Good cooling system: The cooling system for the engine is specifically designed to disperse heat effectively and increase engine lifespan.

Strong compression ratio: The engine’s robust 22.5:1 compression ratio contributes to its increased efficiency and dependability.

Good Lubrication system: The moving elements of the engine are kept lubricated by a good engine lubrication system, which also increases engine life by lowering friction and wear.

Mercedes models using the OM617 engine

You’ll find the OM617 engine under the hood of these models:-

  • W115 series: Mercedes-Benz 220D and 240D models produced between 1968 and 1976
  • W123 series: Mercedes-Benz 200D, 220D, and 240D produced between 1976 and 1985
  • W460 series: The G-Class, also known as the G-Wagen, was a popular off-road vehicle produced by Mercedes-Benz. It was available with the OM617 engine in the 300GD trim.
  • W201 series: Mercedes-Benz 190
  • R107 series: The Mercedes-Benz SL dubbed R107 series had the OM617 engine for models under 280SLD and 350SLD trims.
Best diesel Mercedes engines - OM601 Engine

Best diesel Mercedes engines - OM601 engine

The OM601 is a fantastic engine for practically any application because of its outstanding fuel efficiency, easy operation, and low emissions. It was introduced in the 1980s and was mated to various Benz models until the early 2000s.

The OM601 engine is adaptable and dependable partly because of its relatively simple design. This engine provides the precise ratio of attributes—low fuel consumption and low emissions—that makes diesel engines popular in internal combustion engines.

It was the first in a series of closely related engines – OM601, OM602, and OM603. These families of engines had loads of similarities, but the OM602 and OM603 had turbochargers, making them more powerful than the OM601.

Notable Features Of The OM601 engine

With a displacement of 2.3 liters, this inline 4-cylinder engine is built to last. The most notable features include:-

  • This engine is naturally aspirated. Despite being less powerful than a turbocharged engine, this contributes to its overall durability.
  • A peak power output of around 75 horsepower which is a relatively low power output for its displacement
  • This engine uses a mechanical governor to control engine speed, rather than an electronic control module.
  • Simple design, with few moving parts, which also contributes to its reliability.
  • It has a cast iron block and aluminum cylinder head for optimal strength and thermal efficiency.
  • The OM601 engine has 8 valves, operated by a single overhead camshaft (SOHC)

OM601 engine reliability

One characteristic that aids in reliability is the use of a cast iron block that can withstand high temperatures and pressures without warping or splitting. 

Another feature that contributes to this engine’s dependability is the use of a timing chain rather than a timing belt. Timing chains are known to last the life of the engine, whereas timing belts are known to degrade with time and require replacement regularly.

The OM601 engine also boasts a basic yet effective fuel injection system, which helps with fuel efficiency and pollution.

Based on the factors above, this is an excellent Mercedes diesel engine.

Mercedes models using the OM601 engine

As one of the best diesel Mercedes engines, the OM601 was used in a variety of Mercedes-Benz vehicles, including:-

  • W124 series models – 200D and 230D produced between 1985 to 1993
  • T1 van – Marketed as 208D and 308D models produced between 1977 to 1995
  • 308D Mercedes-Benz Sprinter produced between 1977–1995


Best diesel Mercedes engines - OM 606 engine

Best diesel Mercedes engines - OM 606 Engine

The OM606 was an improvement over the OM601. The power output of the predecessor was not impressive, despite its rated reliability, so this is a significant upgrade.

The OM606 is a 3.0-liter, inline 6-cylinder diesel engine with 24 valves (4 per cylinder) and a single overhead camshaft (SOHC). It’s a turbocharged machine with a Bosch electronic fuel injection system (EFI) that produces around 224 horsepower and 398 lb-ft of torque.

This was one of the best Mercedes inline 6 diesel engines.

This engine is not only powerful but also efficient, as it employs advanced electronic controls to manage engine parameters such as engine speed, fuel injection, and boost pressure. When you’re in the driver’s seat, this engine will make you feel like you’re immortal as you push it to its limits on open roads.

With its cast iron block and aluminum cylinder head for maximum strength, the OM606 engine is built to last. This is a reliable engine.

Notable Features Of The OM 606 engine

The features below depicted a powerful motor back in the day, but depending on who you ask, they could be considered dull today. Nevertheless it made its mark as one of the best diesel Mercedes engines.

This is what distinguished the OM606 as a formidable motor.:-

  • 3.0-liter, inline 6-cylinder engine.
  • 24-valve design, with 4 valves per cylinder.
  • Single overhead camshaft (SOHC) design.
  • Bosch electronic fuel injection system (EFI) and a turbocharger.
  • Advanced electronic engine management controls, such as engine speed, fuel injection, and boost pressure.
  • It employs a common rail fuel injection system, which allows for more precise fuel injection and better combustion.

OM 606 engine reliability

In terms of real-world dependability, the OM606 engine is well-known for its durability and longevity. Many of these engines are still in use with high mileage today. Most have more than 300,000 miles on the odometer. How else can you define dependability, folks?

For engine management, the OM606 engine employs advanced electronic controls. This aids in precise and efficient operation, lowering engine strain and improving performance.

For such a powerful engine, the cast iron block and aluminum cylinder head design are quite clever. The cast iron block gives the engine excellent thermal conductivity and resistance to wear and tear, while the aluminum cylinder head is lightweight for heat dissipation, keeping the engine cool and preventing overheating.

Mercedes models using the OM 606 engine

Between 1993 to 1999 the official production years of the OM606, this engine was mated to the following models:-

  • W124 series cars like the E300 Diesel and E320 diesel models released from 1993 to 1995
  • W210 series where we had the E300 Diesel and E320 diesel models from 1996 to 1999
  • W140 series specifically the S class S320 turbo diesel model from 1996 to 1998
  • The mighty G-Class was also powered by this engine from 1998 to 2001 in the G320 Diesel model

Best diesel Mercedes engines - OM 648 engine

Best diesel Mercedes engines - OM 648 Engine

By the time this powerful, efficient, and reliable diesel engine was released into the market the emission laws were tighter than before. Being a diesel engine it was a swim against the tide for Mercedes. But they still created a gem. 

A couple of nifty features were retained from the previous OM606 like the advanced electronic controls to help optimize the engine’s performance and efficiency. 

With a common rail fuel injection system that allows for better combustion and more precise fuel injection, this diesel engine checked all the right boxes.

Notable Features Of The OM 648 engine

A glimpse at the magic behind the OM648:-

  • 6-cylinder engine that has 24 valves
  • Turbocharger for a power boost 
  • Cast iron block and aluminum cylinder head for optimal strength and thermal efficiency
  • Variable nozzle turbocharger (VNT) which helps for more precise control of the engine’s power output
  • Bosch electronic fuel injection system for better fuel efficiency

OM 648 engine reliability

The engine was built to withstand the rigors of everyday use and to last a long time. The material composition of an engine, the layout, and the power demands all contribute to engine longevity.

The use of a cast iron block and aluminum cylinder head, which is common in related engines, is one of the key features that contribute to the engine’s reliability. There is no need for an explanation.

The engine layout is compact while still allowing for heat dissipation. This also aids in repair and maintenance because parts of the engines deep within are easily accessed.

Plastic parts close to the engine block will cause a slew of problems that are common in modern engines. Although parts like the intake hoses and cover are made of plastic, they are not in direct contact with the block and are not critical components like fuel injectors, so the overall engine integrity is well maintained.

Mercedes models using the OM 648 engine

You’ll find the OM648 diesel under the hood of any of these models:-

  • W211 series in models like the E280 CDI, E320 CDI and E350 CDI models from 2005 to 2009
  • W221 series in models like the S350 CDI, S400 CDI and S280 CDI models from 2006 to 2010
  • W220 series in models like the S320 CDI, S350 CDI, S280 CDI and S320 CDI 
  • W215 series in models like the CL500 CDI, and CL600 CDI models from 2002 to 2006


Wrapping up

Overall, Mercedes-Benz has a long history of producing some of the best diesel engines in the world. The OM601, OM606, OM648, and others each have unique features and strengths that make them suitable for a wide range of vehicles and driving situations. Mercedes-Benz has a diesel engine for you if you need a powerful, efficient, and dependable diesel engine for your car, truck, or SUV.

The high power output, efficiency, and cutting-edge technology of these engines set them apart. If properly maintained, they can easily reach high mileage without major issues.

More on Mercedes Engines

Most reliable Mercedes engines 1

Most Reliable Mercedes Engines

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


mercedes engines to avoid

Mercedes Engines To Avoid

Discover FIVE Mercedes engines to avoid



Best Mercedes E-Class engines

Best Mercedes E-Class Engines

Dive into the Benz world as we find out the best Mercedes E-class engines 

Plus more articles