With Karl Benz, the creator of the first practical motorcar and pioneer of two- and four-stroke engines, you can imagine that Mercedes-Benz has quite a litany of powerplants that have been created over time – and you would be right. These days, the majority are certainly gasoline-powered, but the diesel-powered ones are worth a closer look.
So let’s kick things off by looking at Mercedes-Benz’s inline-four offerings. There’s just a handful of these, starting with the 2.2-liter OM646.
Inline-four: 2.2L OM646, 2.0L OM640, 1.8/2.1L OM651, and 2.0L OM654
Started in 2008, BlueTEC was Mercedes-Benz’s marketing brand denoting the company’s drive toward cleaner diesel motors. Right around the time that selective catalyst reduction (SCR) was introduced to cut down on diesel emissions, BlueTEC was obviously drawn from SCR technology, and no doubt owes its name to the blue diesel exhaust fluid (DEF) from companies like Peak.
BlueTEC was formally introduced at the 2006 North American International Auto Show, where an E-Class and GL-Class showcased the upfitted engines. Shortly thereafter, the Volkswagen Group was licensed to develop its diesel emissions upgrades using BlueTEC technology. And we all know where that went…
The OM646 is a 16-valve, dual overhead camshaft design that succeeded the 1997-2006 OM611. The OM646 was produced from 2002 to 2010, and was found in several models, most notably the E-class sedans. In peak form, it could produce 170 hp and 295 lb-ft of torque.
The OM640 uses common-rail fuel injection, and has a 18:1 compression ratio. It was introduced in 2004 and can be found in A-class compact and B-class hatchback. In peak form, it can produce 140 horsepower and 221 lb-ft of torque.
The OM651 came out in 2008 for the C-class cars, with the aim of meeting Euro 5 standards. Its compound turbocharger setup was an interesting development, and helped the motor make 201 hp and 369 lb-ft of torque.
The OM654 arrived in 2016 for the E-Class, and is comprised of a cast aluminum block, one turbocharger, and Nanoslide coating on the cylinder walls for reduced friction. At its peak, it can produce 195 horsepower and 295 lb-ft of torque. Variants of the motor can be mounted longitudinally and transversely to suit front-wheel-drive, rear-wheel-drive, and all-wheel-drive models.
Far too large for the average car but just right for heavy-duty vehicles, the OM457 has been in production since 2003. It’s water-cooled and is compressed of a cast-iron cylinder block with removable wet-type cylinder liners. Direct injection offers terrific efficiency to the OM457, while still being able to meet Euro 5 emissions standards. At its peak, it makes 449 hp and 1,548 lb-ft of torque.
The bigger brother to the OM457 is the OM473, which was released in 2012. Generating 625 hp and 2,212 lb-ft of torque, yet still compatible with Euro 6 emissions standards, the OM473 was regarded as a landmark achievement by Mercedes-Benz. One point of pride is the X-PULSE fueling system, which adjusts injection from cylinder to cylinder to provide optimum performance. In many regards, it is a beautiful motor.
The last of our inline-six specimens is the OM656, which is practically new for 2017. Trumping the OM642 V6 (which is up next in our overview), this engine sports steel pistons in an all-aluminum engine block, and features a stepped-bowl combustion process that, according to MB, is very good at cutting down on soot (the better to meet Euro 6 emissions standards). It makes 313 hp and 479 lb-ft of torque.
Mercedes-Benz has had a variety of diesel V6s over the years, but we’ll just be going over two of them. The first of these is the 12-liter OM501, which was made for the Euro 2 era of 1996-99. It had an air-to-air intercooler and was turbocharged, and made 394 hp and 1,364 lb-ft of torque to power 18-wheelers.
More modern but definitely downsized is the OM642, introduced in 2005. At three liters of displacement, it could never be powerful enough to chug through an Alpine road with 20,000 pounds of tree trunks in the back, but it could definitely service such cars as the E-Class, C-Class, G-Class, and even the European versions of the Jeep Commander and Grand Cherokee. It’s since been overshadowed by the aforementioned OM656, and will be phased out soon.
At the turn of the millenium, Mercedes-Benz launched a diesel V8 called the OM628. The engine had a cast aluminum block and cast iron cylinder liners, and had a compression ratio of 18.5:1. Turbocharged, air-to-water intercooled, and with four valves per cylinder, the OM628 was quite efficient and could make up to 260 hp and 413 lb-ft of torque. It was found in several vehicles, including the S-Class, G-Class, and E-Class.
The follow-up to the OM628 was the OM629, debuting in 2010. It had the same four liters of displacement, but had improvements to the common-rail direct injection system, as well as a greater charge from twin turbochargers. This allowed the OM629 to generate up to 320 hp and 538 lb-ft of torque.
You’ll have to forgive us here, from from the V10 on, the internet’s breadth of information on Mercedes diesel engines reaches a breaking point; it all becomes ad listings or main bearing torque specifications. Nevertheless, we were able to dig up a little bit on this radical V10 – the OM443.
Part of the 400 series, the OM443 was the successor to the OM441A. We’re not sure of the exact dates that it entered production, but given that it was made to meet the 1996-99 Euro 2 standards, we can see that it was used during the 1990s and likely up through the early 2000s.
In terms of technical aspects, the OM443 could make 536 hp and 1,622 lb-ft of torque. It weighed about 2,250 pounds, and had a compression ratio of 16.9:1. It was installed into combine harvesters, box trucks, and most likely busses and 18-wheeler trucks.
We’re breaking the rules to bring you this last one (since it’s not a modern-era diesel motor), but we think it’s well worth it. The MB518, a V20 capable of displacing over 134 liters of air in a full cycle, was a beast of a powerplant.
Manufactured from 1951 to 1973, the MB518 went through a few updates, the last of which (Model D) was in 1968. At that point, it could make 3,500 horsepower and an ungodly 8,800 lb-ft of torque! This gave the MB518 a power-to-weight ratio of 1hp/3.31 lbs. We can only imagine what this monster sounded like.
The SeaStar, a 44-meter yacht built in 2007 from a 1963 German Navy vessel. It features four MB518s, making it capable of doing up to 42 knots (48mph) on water!
The engine found its way into German Navy boats during the Cold War, some of which have since been converted into luxury yachts. One example we found was the Sea Star, a 44-meter specimen powered by four MB518s, allowing the ship to reach up to 42 knots (or 48mph).
Looking back over these Mercedes-Benz diesel mills, we’ve gotten a good look at just a few examples of what the automaker could do. The company made some terrific advancements over the years, but we want to know – which MB diesel engine is your favorite? Let us know in the comments below.