Engine Code Decoder — Mercedes-Benz Engine Code Guide

Q: What does the "OM" in a Mercedes engine code stand for?

"OM" stands for Öl-Motor (oil engine) – that is, a diesel engine. "M" stands for Motor (petrol engine). This distinction is crucial for ordering correct parts.

Q: Why does my engine code have a "DE" suffix?

"DE" stands for Direct Injection (Direkteinspritzung). It indicates fuel is injected directly into the combustion chamber, common on modern Mercedes engines for efficiency and emissions.

A Mercedes engine code — such as M272, OM651, or M276 — is your key to identifying the exact engine in your car. The code tells you the family, displacement, fuel type, and generation, which is essential for ordering correct parts, understanding service intervals, and evaluating replacement options.

M = petrol (Motor) · OM = diesel (Öl-Motor) · AMG = high‑performance variants
Modern codes (e.g., M256, OM654) use a 3‑digit numbering system with suffix letters for variants
Engine number is stamped on the block and also appears on the VIN and vehicle documents
Use this decoder to match your code to displacement, power, and common failure patterns
Last verified: February 2026

Full decoding table, location guide, common mistakes, and practical verification steps below.

What a Mercedes Engine Code Tells You

The engine code is more than a random string — it encodes the engine's family, configuration, and often its displacement and generation.

Prefix: M for petrol (e.g., M272, M276), OM for diesel (e.g., OM651, OM642). AMG engines (e.g., M156, M157) are petrol‑based performance variants.
Number: The three‑digit number indicates the engine family; higher numbers are generally newer. For example, OM651 is a 2.1‑litre 4‑cylinder diesel; OM654 is the newer 2.0‑litre modular diesel.
Suffix letters (e.g., DE, LA) denote additional features — direct injection, turbocharging, or specific market variants. For instance, OM651 DE22 LA means diesel, direct injection, 2.2 litres, turbocharged.
Displacement: Often implicit. M272 is a 3.5‑litre V6; M276 is a 3.5‑litre V6 (later generation); OM642 is a 3.0‑litre V6 diesel.

Knowing your engine code is the first step to any maintenance or repair — it ensures you order the correct oil filter, timing chain kit, or even a full replacement unit.

Where to Find Your Mercedes Engine Code

The engine code is stamped on the engine block and can also be found on the vehicle identification plate and in the VIN.

Engine block stamp: On most Mercedes engines, the code is stamped on a flat pad on the side of the block — often near the starter motor or on the right‑hand side (viewed from the driver's seat). For example, on the OM651, it's visible from above behind the injectors.
Vehicle data plate: Located on the driver's side door pillar (B‑pillar) or inside the engine bay on the strut tower. It lists the engine code under "Motor" or "Engine".
VIN (Vehicle Identification Number): The 6th‑8th digits of the 17‑character VIN encode the engine variant. Use our VIN Decoder to pull the exact engine code from your VIN.
Service booklet / digital service history: The engine code is often recorded in service records.

If you can't locate the stamp, the VIN is the most reliable alternative — it never wears off.

Mercedes Engine Code Decoding Table

Below is a selection of common Mercedes engine codes, their displacement, fuel type, typical applications, and notable characteristics.

Code	Family	Displacement	Fuel	Typical Applications	Notes
M272	V6 petrol	3.0‑3.5 L	Petrol	E‑Class (W211), C‑Class (W204), ML (W164)	Balance shaft issue on early units
M276	V6 petrol	3.0‑3.5 L	Petrol	E‑Class (W212/W213), C‑Class (W205), GLC	Improved over M272; camshaft adjuster wear
OM642	V6 diesel	3.0 L	Diesel	E‑Class (W211/W212), ML (W164), Sprinter	Swirl flap and oil cooler seal issues
OM651	4‑cyl diesel	2.1 L	Diesel	C‑Class (W204/W205), E‑Class (W212), GLC	Balance shaft and injector seal failures
OM654	4‑cyl diesel	2.0 L	Diesel	E‑Class (W213), C‑Class (W206), GLC (X253)	Modern modular diesel; AdBlue system
M157	V8 petrol (AMG)	5.5 L	Petrol	E‑Class (W212), CLS, S‑Class (W221), ML	Hot‑vee design; known for timing chain and valve seal wear
M178	V8 petrol (AMG GT)	4.0 L	Petrol	AMG GT, S‑Class (W222), E‑Class (W213)	Modern twin‑turbo; generally robust
M270	4‑cyl petrol	1.6‑2.0 L	Petrol	A‑Class (W176), B‑Class (W246), CLA	Turbocharged; timing chain tensioner issues
M274	4‑cyl petrol	2.0 L	Petrol	C‑Class (W205), E‑Class (W213), GLC	Successor to M270; improved chain design
OM646	4‑cyl diesel	2.1 L	Diesel	C‑Class (W203), E‑Class (W211), Sprinter	Pre‑OM651; injector seal and EGR issues

This table is a summary. For full details on a specific engine, visit its dedicated Engine Knowledge Centre.

Notes & Caveats

Generation variations: Same engine code may have revisions that differ in internal parts (e.g., timing chain guides, injector types). Always check the engine number suffix (e.g., OM651.900 vs .958) for exact compatibility.
Facelift changes: Mid‑life updates often change the engine code even if displacement remains the same. For example, the M276 replaced the M272 in many models after 2012.
Market differences: US‑spec engines may have different emissions equipment and slightly different codes (e.g., M276 DE35 vs M276 DE35LA). UK/EU codes typically follow the European naming.
AMG differentiation: AMG engines often share the same base number but have a separate code (e.g., M156 is the 6.2‑litre V8 AMG, while the standard M273 is 5.5‑litre).

Common Mistakes

Confusing M and OM: A petrol engine code starts with M, diesel with OM. Ordering parts for the wrong fuel type is a costly error.
Ignoring suffix letters: DE (direct injection) and LA (turbocharged) can indicate different injectors or fuel systems – matching only the base code may lead to incompatible parts.
Assuming same code across model years: An OM651 in a 2010 E‑Class may have different torque and emissions hardware than one in a 2016 GLC; always verify the exact engine number.
Using aftermarket databases without cross‑checking: Some online decoders provide generic information that may not match Mercedes‑specific variations. Always confirm with official data or our VIN Decoder.

How to Verify Your Engine Code

To be absolutely certain of your engine code, follow these steps:

Check the vehicle data plate (B‑pillar) – it lists the engine code clearly.
Look for the stamp on the engine block – it's usually on a flat machined surface near the starter motor or on the side of the cylinder head.
Use the VIN – decode the 6th‑8th characters using our VIN Decoder; this gives the exact factory specification.
Compare with the service history – if the car has had an engine replacement, the code may not match the VIN; verify both.

If you're still unsure, our Diagnostic Wizard can guide you through identification based on model, year, and known configurations.

Why This Specification Matters

The engine code is the single most important piece of information for any repair or maintenance task. It dictates which oil filter, timing chain, injectors, and even which engine oil grade (viscosity and specification) to use. Ordering the wrong part because of an incorrect code can lead to misfits, premature wear, or catastrophic failure.

For example, the OM651 diesel engine has multiple revisions – early versions have a known balance shaft issue, which is corrected in later variants. Knowing the exact code allows you to check if your engine falls within the affected range and plan preventive maintenance accordingly, as detailed in our OM651 balance shaft failure page.

Similarly, the M272 V6 petrol engine is notorious for the balance shaft timing chain sprocket failure; identifying your engine as M272 (especially pre‑2010) alerts you to monitor for symptoms. This decoder is not just a reference – it's a diagnostic starting point.

Related Specifications

Engine Number Location Guide →

Detailed photos and instructions for finding the stamp on each engine family.

Mercedes Fitment Matrix →

Which engines fit which models – essential for replacements.

OM651 Oil Capacity & Spec →

Correct oil specification for the 2.1‑litre diesel.

M272 Oil Capacity →

Oil spec and capacity for the 3.5‑litre V6 petrol.

VIN Decoder Tool →

Decode your VIN to get the factory engine code instantly.

Failure Rate by Engine →

Data‑backed reliability of each engine family.

Frequently Asked Questions

What does the "OM" in a Mercedes engine code stand for?

"OM" stands for Öl-Motor (oil engine) – that is, a diesel engine. "M" stands for Motor (petrol engine). This distinction is crucial for ordering correct parts.

How can I find my Mercedes engine code without looking under the bonnet?

You can use the VIN – the 6th‑8th digits encode the engine variant. Alternatively, check the vehicle data plate on the driver's door pillar, or use our VIN Decoder tool for an instant result.

Do all Mercedes engines with the same code have identical parts?

Not always. Revisions (e.g., OM651.900 vs .958) can have different timing chains, injectors, or EGR systems. Always verify the full engine number when ordering parts.

What is the difference between M272 and M276?

M272 is an earlier 3.0‑3.5‑litre V6 petrol, known for balance shaft issues. M276 is the successor, introduced around 2010, with improved timing chain guides and better reliability.

Why does my engine code have a "DE" suffix?

"DE" stands for Direct Injection (Direkteinspritzung). It indicates fuel is injected directly into the combustion chamber, common on modern Mercedes engines for efficiency and emissions.

Can I replace my engine with a different code that has the same displacement?

Possible, but not straightforward. Different engine codes may have different mounting points, wiring harnesses, and ECU mappings. Consult a specialist and our Fitment Matrix before considering a swap.

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Verified DataCross‑checked with Mercedes‑Benz technical documentation and specialist workshops.

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Last Verified February 2026Regularly updated to reflect the latest engine codes and revisions.

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15+ Vetted SpecialistsReal‑world insights from Mercedes specialists across the UK.

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100% IndependentNo manufacturer or dealer bias – pure technical reference.

Engine Code Decoder — Mercedes Engine Code Guide