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The AMG brand has undergone several evolutions over the years dedicated to building the most developed Mercedes vehicles money can buy. Racing fame in the seventies gave way to the tuner boom of the eighties, where they captured the hearts and minds of many an enthusiast. Their acquisition by Mercedes in the nineties cemented their connection to the brand, and they’ve been a household name ever since. Paramount to their reputation are the tuned engines that turn gasoline into earth-moving torque and a thunderous soundtrack. Though, I should say that that’s every AMG model but one. What few in the ‘States realize is that for a brief time under the Mercedes banner, AMG strayed from tradition and put their engineering expertise into a diesel.

 

The W203 C-Class

Mercedes’ W203 C-class was a hit all over the globe, modernizing the entry-level sedan across the globe for the 21st century. The new model brought about a fresh redesign and new tech that shed the ‘90s boxiness for a more rounded shape that sported one of the most iconic headlight styles of the era. Examples were available in the traditional estate and sedan formats and the all-new “SportCoupé” variant—a shortened, two-door hatchback that emulated BMW’s earlier E36 318ti. 

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Among the nearly dozen trims offered in the US over its lifespan, it’s best remembered for its quickest AMG variant, the C55. For the latter half of production, the modest sedan was given the traditional AMG treatment; a stylishly aggressive body kit, big wheels and brakes, and an angry, high-displacement V8. As with all AMG models, its engine was the focal point, and, in this case, was the 5.4L M113. Its sounds and power made it the perfect power plant, as it provided the luxury smoothness and brute force that every modern AMG machine is given, and it’s that characteristic that makes the C30 CDI AMG, the only diesel-equipped model to leave the hallowed halls in Affalterbach post-merger, such an oddity. 

 

Diesel Development

Americans and Europeans have very different experiences with diesel powertrains. Decades ago, Euro policymakers placed higher taxes on gasoline (petrol in euro-speak), making diesel the fuel of choice. That couldn’t be farther from the status quo across the pond, where diesel is almost exclusively associated with trucks of all sizes. But the European mindset has spawned many greats and more than a few oddities. 

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As the 2000 model year rolled around, Mercedes’ diesel tech and the US’s adoption of it were heading in different directions. The W210 E300dT didn’t make it past the mid-cycle refresh the year prior, starting a six-year gap in which no diesel-powered Mercedes were sold in America. On the other side, the engineers in Stuttgart modernized all models wearing the small “d” badge with a new series of engines featuring CDI, common rail direct injection. Funky name aside, the new injection system provided an enormous leap forward in slashing fuel consumption and improving performance. 

Whether that’s what got the interest of AMG or not, we don’t know, but one of those new engines, the OM612 turbocharged inline 5-cylinder from a Sprinter van, ended up in their famous workshop for a thorough lookover. 

 

The Mercedes-Benz C30 CDI AMG

Alongside the M112 E32ML V6, which would also get performance modifications for the C30’s gasoline-powered sibling, the C32, the diesel inline-5, was tested and stripped apart for transformation. Starting with the internals, AMG chucked the standard crankshaft in the bin and fitted a stronger one that increased stroke from 88.3mm to 97mm, resulting in a displacement bump to 3.0L. That alone would add power, but it’s far from all that was done. There were also modifications to the cylinder head, stronger pistons, an air-to-water intercooler, and a redesigned glow plug system which featured a shorter pre-glow time and higher annealing temperature. For reliability’s sake, a larger volume oil pump and piston oil squirters kept the tuned mill happy and healthy.

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Altogether, it was a vastly improved engine with impressive performance figures for the day. On paper, the 228 hp figure isn’t very intimidating, but diesels aren’t known for their horsepower; the 398 lb-ft of torque figure made the C30 AMG more than just an exercise in what could be. Mated to an AMG-tweaked 722.6 5-speed auto, it hit 60mph in a respectable 6.8s and reached an electronically limited 155 mph. Those were significant figures for the day and boosted to those heights by the C30’s unique turbocharger. Larger than the one fitted to the standard OM612, it used electronically controlled vanes on the hot side to reduce spool times and provide a better top end.

Of course, in true AMG fashion, it wasn’t just about the engine but a complete overhaul of all systems. As such, the C30 benefitted from much more than a new engine. Bespoke sport suspension tuning, large brakes, and 17” AMG wheels meant the sporty diesel had the handling prowess to back up the badge, while the aggressive yet subtle exterior treatment let it stand out without the wild wings and flares of rivals. It was a high-performance luxury sport sedan capable of starting a new kind of enthusiast vehicle.

But that didn’t happen. 

It was slower than its C32 sibling and other Euro sports sedans like the M3 and S4, and its hefty curb weight—in this case, 3615 lbs—put it several hundred lbs above all but the Audi, attributing to the comparatively worse performance. Plus, with a base price nearing $71,000 in today’s money and bits like leather upholstery and a CD changer remaining optional extras, buyers were left asking, “Why?” Similar useability, more features, and better performance were available elsewhere for less, so the diesel AMG was not a hit among buyers.

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In its four-year run that ended in 2004, just 691 examples left Affalterbach across the three body styles, with the SportCoupé being the best seller. The potential was there, but buyers were clearly put off by the value, not to mention the relatively novel idea of an oil-burning sport luxury sedan. It’s likely that bringing it over to North America wouldn’t have yielded any better results either, as it would’ve been even more foreign to potential buyers. Instead, it remains an AMG oddity and a fun choice for importation in a few years.  

Looking back, the Merc was one of a few models pushing the diesel performance boundaries—the others being the Touareg and Q7 with the 5.0L twin-turbo V10 and 6.0L twin-turbo V12, respectively. However, it now appears as though it was simply ahead of its time as Audi, VW, and BMW have all embraced the diesel in some performance-oriented capacity. At the very least, the C30 CDI AMG walked so the quad-turbo X5 M50d, B9.5 S4, and C8 S6 could run.


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Written by :
Christian Schaefer

Car and motorsports-obsessed writer/editor for FCP Euro's DIY Blog. Constantly dreaming of competing behind the wheel or searching for another project. Owner of a turbo Subaru Forester and a ratty Porsche 914, neither of which are running.


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