Mercedes W124 Diesel —
The Most Durable Chapter of the Series
Engine families, every model from 200D to 300D Turbo, buying advice, and what makes the W124 diesel practically indestructible to this day.
When you talk about the Mercedes W124, at some point you talk about diesel. Not because the petrol engines are uninteresting — but because the diesel engines of this series tell their own story. A story about common sense that still has character. About durability that today sounds like a legend. And about engines built at a time when Mercedes still built as if every vehicle had to run forever.
The short version: The W124 relied on three robust pre-chamber diesel units (OM601, OM602, OM603) with no timing belt and legendary mileage. The diesel variants remain the best-selling representatives of the series to this day — and have long since become sought-after classics with their own H-plate eligibility.
The diesel variants of the W124 remain the best-selling representatives of the series to this day — and have long since become sought-after classics in their own right.
The Engine Families: OM601, OM602, OM603
Before understanding the individual models, you need to know the engines. Mercedes relied on three diesel units in the W124, all stemming from the same engineering philosophy: pre-chamber diesel technology, cast-iron blocks, chain instead of belt drive. Robust, easy to maintain, built for eternity.
| Engine | Cylinders | Displacement | Character |
|---|---|---|---|
| OM601 | 4-cylinder | 2.0 litres | The smallest of the three — solid down to the last screw |
| OM602 | 5-cylinder | 2.5 litres | The exotic one — smoother than the four-cylinder, also existed as a turbo |
| OM603 | 6-cylinder | 3.0 litres | The flagship — silky-smooth running, legendary for 600,000-km mileages |
OM601 — Four-cylinder, 2.0 litres. The smallest of the three. Four cylinders, pre-chamber injection, solid down to the last screw. Not a sports engine, but one that spells out the word "durability" like no other.
OM602 — Five-cylinder, 2.5 litres. The exotic of the family. Five cylinders are rare in diesel engines — in the W124, they're a distinguishing feature. The OM602 runs smoother than the four-cylinder and pulls harder than its displacement number suggests. It also existed as a turbo variant.
OM603 — Inline six-cylinder, 3.0 litres. Six cylinders, silky-smooth running, the flagship of the diesel range. The OM603 is the engine taxi drivers tell legends about: 600,000 kilometres, first gearbox still original. With a turbocharger it became the most powerful production diesel Mercedes had built to that point.
The Models in Detail
200D — the Sensible One
Engine: OM601 · 2.0 litres · 4-cylinder · 72 hp
Years built: 1984–1993
The 200D is the most-built diesel model of the W124 and the car you used to see everywhere — and can barely find today. What was once seen as a pure workhorse has become a rare piece of living history.
72 hp sounds like little — and it is. The 200D never claimed to be sporty. It drives. It runs. It stops. On the motorway it manages just under 160 km/h, already a feat for this engine. But it does so with a reliability modern vehicles can only dream of.
What makes it a classic is exactly this down-to-earthness: no turbo, no complexity, no weakness. Find a well-preserved 200D and you've found a vehicle that could still run for another 30 years.
250D — the Five-Cylinder Insider Tip
Engine: OM602 · 2.5 litres · 5-cylinder · 90 hp
Years built: 1985–1993
The 250D is the model connoisseurs choose. A five-cylinder diesel is a rarity in this class — and it makes itself known. Sit in a 250D and start the engine, and you'll hear the unmistakable clatter of a five-cylinder: slightly asynchronous, slightly rough, entirely its own thing.
With 90 hp it's noticeably more confident in daily use than the 200D. Motorway distances are relaxed, fuel consumption stays reasonable. Mechanically the OM602 is considered just as indestructible as its siblings — well-maintained examples comfortably clear 400,000 kilometres.
Today the 250D sits slightly in the shadow of the bigger six-cylinders, which often makes it cheaper on the market — unfairly so.
300D — the Six-Cylinder Classic
Engine: OM603 · 3.0 litres · 6-cylinder · 109 hp
Years built: 1985–1993
The 300D is the diesel Mercedes enthusiasts go looking for. Six cylinders running so smoothly you almost forget it's a diesel. The OM603 is quiet, cultivated — a diesel with manners.
109 hp is entirely sufficient for the car's class and weight. The 300D glides rather than pushes. It's not a car for the impatient — but for people who know the journey itself is the point.
As an estate (S124/300 TD), the 300D has become a full-blown institution. The wagon body, the inline six, the W124 chassis — a combination that still doesn't roll onto a campsite unnoticed.
300D Turbo — the Most Powerful Diesel of the Series
Engine: OM603 with exhaust turbocharger · 3.0 litres · 6-cylinder · 143 hp
Years built: 1987–1993 (saloon), later also as an estate
The 300D Turbo is what happens when an already excellent engine gets a turbocharger. 143 hp from a production diesel of that era was a statement when it launched in 1987. Mercedes not only had the most powerful production diesel in its own lineup, but one of the most powerful worldwide.
The turbo makes the OM603 noticeably punchier in the mid-range. The turbo lag typical of the era is present — wait for boost, and you're rewarded. On the motorway the 300D Turbo moves with a confidence that clearly leaves the naturally aspirated version behind.
Mechanically the turbo variant is somewhat more demanding to maintain than the naturally aspirated one — turbocharger, intercooler and injection system need regular attention. Give it that, and you own one of the most sought-after W124s there is.
The 200D and 250D are the most parts-friendly and affordable entry-level models. Want more confidence in daily driving? Go for the 300D. The 300D Turbo is the most coveted but also the most maintenance-intensive variant — a car for connoisseurs.
After the Facelift: the E-Class Diesels (1993–1995)
From 1993 onward, the W124 officially carried the "E-Class" designation — and the diesel model names switched to the scheme still used today. The 250D became the E 250 Diesel, the 300D became the E 300 Diesel, and the 300D Turbo became the E 300 Turbodiesel.
Technically, little changed under the facelift models — the series was already fully matured in its final production years. Externally, the facelift brought revised bumpers, new door mirrors and a refreshed interior. Collectors value both generations; the pre-facelift is seen as visually cleaner, the facelift as slightly cosier inside.
What All W124 Diesels Have in Common
Four core engineering principles run through the entire W124 diesel line-up — and explain why these engines remain so indestructible to this day.
What to Watch Out for When Buying
W124 diesels forgive a lot — but not everything. These four points decide between a good purchase and an expensive mistake.
Dry your W124 thoroughly after every wash — moisture trapped in door seals and sills is the most common trigger for exactly the kind of rust these engines otherwise take so long to develop. A quality microfibre drying towel of at least 800 GSM prevents scratches in the original paintwork and lifts water efficiently without wiping.
- ✓ 1600 GSM — dries an entire vehicle in one pass
- ✓ No micro-scratches on sensitive original paint
- ✓ Streak-free finish on the first wipe
Conclusion: Diesel That Lasts
The W124 diesels aren't cars for people who want attention. They're cars for people who know what quality means — and are willing to drive slowly for it.
What these engines achieve is no accident. It's the result of an engineering culture that is itself history now. Anyone who finds a well-maintained 300D or a rare 250D today finds more than a car. They find a statement — built in steel, cast iron, and the conviction that a vehicle has to last.