Mercedes-Benz OM656

OM656 Engine

The OM656 is a 3.0-liter inline-6 diesel engine, widely regarded as one of the finest diesel engines Mercedes-Benz has ever produced. It replaced the V6 OM642. Featuring a stepped-bowl combustion process and two-stage turbocharging, it delivers impressive power and refinement while meeting strict emissions standards.

This overview summarizes the reliability of the Mercedes-Benz OM656, including common issues and cost drivers.

Mercedes-Benz OM656 engine — Image credit: Wikimedia Commons · CC BY-SA 4.0

Technical Specifications

Manufacturer

Mercedes-Benz

Fuel Type

Diesel

Displacement

3.0 L

Production

2017–Present

Power Output

286–340 hp

Emissions

Euro 6d

Reliability Analysis

The OM656 is a masterpiece of diesel engineering, with a risk score of 4.5/10. It is generally very reliable, with few reported mechanical weaknesses. The main issues are related to the emissions systems (DPF/AdBlue), which is standard for the class. It is a highly recommended engine for those covering higher mileages.

Common Problems & Weak Points

Issue	Typical Mileage	Repair Cost (Est.)	Severity
DPF Regeneration Issues	~120,000 km	€1000 – €2000	Medium

DPF Regeneration Issues

Like most modern diesel engines, the OM656 is equipped with a Diesel Particulate Filter (DPF). Frequent short trips or city driving can prevent the DPF from reaching the temperatures needed for regeneration, leading to clogging. This can result in warning lights and reduced performance. A forced regeneration or professional cleaning may be required, costing between 1000 and 2000 Euros.

Typical Mileage: 120,000 km

Cost: €1000–2000

Buyer's Inspection Checklist

Check for DPF warning lights or messages indicating regeneration is needed.
Verify that the car has been driven on highways regularly, which helps keep the DPF clean.
Inspect for oil leaks, though they are uncommon on well-maintained units.

Frequently Asked Questions

Is the OM656 engine reliable?

The OM656 has known weak points, but with good maintenance the reliability is solid. See the risk analysis and common problems for specifics. Start a report for a specific car.

How expensive are typical repairs?

Common repairs fall into a mid-range cost band depending on the issue and workshop. Check the cost ranges in the table. Use the used car report for specific listings.

Which model years are best for this engine?

Newer production years often include technical updates. Review the production years and revisions in the specs. Use Car Check for quick screening.

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