The Mercedes OM602 Diesel
The OM602 is a 2.5L liter, inline-five Mercedes-Benz diesel engine developed in the late 1980s. Known as one of the most reliable diesel engines Mercedes ever produced, it was equipped in many different models including select passenger cars, light commercial platforms, and the G Class Gelandewagen. It became a staple for its mechanical simplicity, steady torque delivery, and long service life, traits that made it perfect for later application in military vehicles.
Enjoy a look into the "million-mile" engine and its different use-cases, technical specs, and history.
OM602 Specs and Technical Details
Configuration: Inline-5, SOHC, indirect injection (mechanical)
Displacement: 2,497 cc (2.5 L); later family variants included 2.9 L
Induction: Naturally aspirated (OM602) and factory turbocharged versions (often referenced as OM602a)
Output (typical): ~90–94 hp NA; ~120 hp in turbo applications (market/trim dependent)
Block/Head: Cast-iron durability with straightforward service access
Known strengths: Thermal stability, consistent lubrication and cooling under load, parts availability
Service window: Produced across multiple platforms from the mid-1980s through the early 2000s (markets vary).
Original Applications (Where You’ll Find It)
The OM602 appeared across several chassis families, including:
G Class (W460/W461): Prominently known for its use in the 250GD military Wolf. Dependability, serviceability, and off-road performance made it ideal for utility and military roles.
Passenger cars: 190 2.5 and 190D 2.5 Turbo (W201), 250D and 300D 2.5 Turbo (W124), and E290 Turbodiesel (W210) which used the 2.9L variant.
Light commercial platforms: Mercedes 210D, 310D, 410D and early Sprinter Phase 1 (D12D and 412D) utilized the 2.9L OM602 featuring direct-injection version in some vans.
Reliability and Real-World Reputation
The OM602 developed a reputation as the “million-mile” diesel. Mechanical injection, robust internals, and conservative factory tuning contribute to engines that commonly run very high mileage with routine maintenance. While it is not the highest-output diesel of its era, it is notably tolerant of temperature swings and extended operation, one reason it served in military 250GD Wolf duty cycles.
In stock configuration, the OM602 delivers linear, usable torque with modest peak power. In a Gelandewagen diesel, that translates to predictable throttle response and steady progress on grades or trails. Turbocharged variants add headroom for highway cruising without changing the character of the drivetrain.
OM602 vs. Other Mercedes Diesels (Quick Context)
OM605 (2.5-L inline-five turbodiesel): Later generation with stronger stock output and tuning headroom; still closely related in architecture.
OM606 (3.0-L inline-six turbodiesel): DOHC design and higher potential; favored in performance-oriented diesel builds.
Where the OM602 fits: Most “authentic” for a 250GD Wolf restoration that prioritizes period-correct feel and authenticity over outright power. (Think accurate, analog torque rather than top-end thrust.)
The OM602 in G Wagon Restorations
For a period-correct Wolf, the OM602 remains a first-choice engine. It preserves the original feel of a 250GD while delivering the reliability expected from a classic utility platform. In Custom G Wagon builds, owners choose the OM602 to keep the truck’s military-era character intact, especially in short-wheelbase and convertible G Wagon configurations where analog engagement is part of the appeal.
Favor modern or rare variants? Hyper-luxury specials like the 620GE G Wagon from Expedition Motor Company offer the power of an LS3 V8 gasoline engine in an authentic 250GD restoration.
Notable Details for the G Class Enthusiast
Cooling and lubrication: Designed for continuous load; critical for low-speed, high-traction work.
Fuel system: Mechanical indirect injection aids cold starts and field serviceability.
Transmissions: Paired with 5-speed "iron box" manuals from factory.
Chassis pairing: Works naturally with locking diffs, low-range gearing, and the ladder-frame of classic Gelandewagen G Class models, particularly W460/W461.
FAQs
Is the OM602 underpowered by modern standards?
In practice, its steady torque and gearing make it well-matched to classic G Wagon use, especially in W460/W461 trucks.
Can the OM602 cruise at highway speeds?
A well-maintained OM602 with correct gearing and tire choice can maintain typical highway speeds.
How does it compare to the OM606 for swaps?
The OM606 offers more power and tuning headroom. The OM602 is simpler, lighter, and more “period-correct” for many restorations focused on originality.
Is it suitable for a short-wheelbase cabrio?
Yes. In a two door G Wagon (SWB), the OM602’s linear delivery suits open-air, lower-mass builds and preserves driving character.
Conclusion
The OM602 is the dependable heart of many classic Mercedes 250GD Wolf builds. It preserves the mechanical cadence and serviceable simplicity that define a vintage G while remaining flexible enough for daily use. Whether you’re researching a Mercedes W460, considering a convertible G Wagon, or planning a Custom G Wagon with period-correct hardware, the OM602 remains a credible, authentic choice for a classic G Class.