The Mercedes-Benz M115.972 is a 2,778 cc, inline-six, naturally aspirated petrol engine produced between 1968 and 1976. It belongs to the M115 engine family, featuring a single overhead camshaft (SOHC), hemispherical combustion chambers, and a twin-choke Solex 4A1 DVG carburettor. Delivering 120 kW (163 PS) at 5,500 rpm and 230 Nm of torque at 3,800 rpm, it offered refined performance with enhanced low-end responsiveness compared to earlier variants.
Fitted primarily to the W114 280 and W115 280 models, the M115.972 was engineered for balanced driving dynamics, combining smooth power delivery with increased torque for improved overtaking capability. Its design prioritised mechanical durability and passenger comfort, making it suitable for mid-size executive applications. Emissions control relied on precision carburettor calibration and crankcase ventilation, meeting pre-regulatory European standards of the era.
One documented technical update involves revisions to the camshaft drive system introduced in 1972, addressing premature wear observed in early production units. This improvement, detailed in Mercedes-Benz Service Information Bulletin 03.0201, enhanced oil flow to the front-mounted timing chain tensioner. Later models incorporated this revised tensioner assembly, improving long-term reliability under sustained operation.
Production years 1968–1976 comply with pre-Euro emissions standards as defined under ECE Regulation 15 (Revision 01). Vehicle Certification Agency (VCA) Type Approval records confirm conformity for UK-market variants.
The Mercedes-Benz M115.972 is a 2,778 cc inline-six petrol engine developed for mid-size executive saloons (1968–1976). It features SOHC valvetrain architecture with twin-choke carburettor induction, delivering linear power delivery and mechanical refinement. Designed prior to modern emissions regulations, it balances period-correct performance with long-term durability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,778 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-6, SOHC, 12-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 74.0 mm | |
| Power output | 120 kW (163 PS) @ 5,500 rpm | |
| Torque | 230 Nm @ 3,800 rpm | |
| Fuel system | Twin-choke Solex 4A1 DVG carburettor | |
| Emissions standard | Pre-regulatory (ECE R15-01) | |
| Compression ratio | 8.7:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven (duplex), front-mounted | |
| Oil type | SAE 20W-50 mineral (API SF/CC) | |
| Dry weight | 192 kg |
The SOHC inline-six layout provides smooth power delivery ideal for relaxed cruising, but requires adherence to 15,000 km oil change intervals using SAE 20W-50 mineral oil to maintain camshaft and chain longevity. Correct carburettor synchronization is essential for idle stability and fuel efficiency. The front-mounted duplex timing chain is robust but early tensioner designs are susceptible to wear under aggressive driving; post-1972 units benefit from an upgraded tensioner per Mercedes-Benz SIB 03.0201. Cooling system integrity must be maintained—original thermostats and water pumps should be inspected regularly to prevent overheating. Use of ethanol-blended fuels is discouraged due to compatibility issues with vintage fuel system materials.
Oil Specs: Requires SAE 20W-50 mineral oil meeting API SF/CC (Mercedes-Benz SIB 03.0201). Modern equivalents acceptable if viscosity and additive profile match.
Emissions: Pre-regulatory compliance under ECE Regulation 15 (Revision 01) applies to all production years (VCA Type Approval #VCA/MER/68-115). No Euro standards existed during production period.
Power Ratings: Measured under DIN 70020 standards. Output verified on factory-original tune with correct carburettor jetting and ignition timing (Mercedes-Benz TIS A115-715).
Mercedes-Benz Technical Information System (TIS): Docs A115-680, A115-715, SIB 03.0201
VCA Type Approval Database (VCA/MER/68-115)
DIN 70020 Engine Power Measurement Standard
The Mercedes-Benz M115.972 was used across Mercedes-Benz's W114/W115 platforms with longitudinal mounting and no licensing partnerships. This engine received platform-specific adaptations-tuned intake manifolds for saloon versus coupe applications-and from 1972 the updated W114.020 series adopted revised valve train components, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the left-side cylinder block near the bellhousing flange (Mercedes-Benz TIS A115-680). The 7th and 8th digits of the VIN indicate engine type ('15' for M115 series). Pre-1972 models have chrome valve covers with ribbed design; post-1972 units use matte-finish covers. Critical differentiation from M114: M115.972 features a single Solex carburettor and 8.7:1 compression, while M114 variants use twin Zenith carburettors with higher compression. Service parts require chassis number verification—timing chains for pre-1972 production are incompatible with later units due to tensioner redesign (Mercedes-Benz SIB 03.0201).
The M115.972's primary reliability risk is timing chain tensioner wear on early builds, with elevated incidence in high-mileage or poorly maintained examples. Internal Mercedes-Benz service reports from 1973 noted increased chain noise in pre-1972 units exceeding 100,000 km, while VCA inspection records show a notable share of emissions-related failures linked to carburettor imbalance in vintage vehicles. Extended oil change intervals and use of incorrect viscosity oils accelerate wear, making adherence to factory service intervals critical.
Analysis derived from Mercedes-Benz technical bulletins (1968-1976) and UK DVSA vintage vehicle inspection statistics (2018-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M115972.
Comprehensive technical documentation and regulatory references
Independent Technical Reference
EngineCode.uk is an independent technical reference platform operated by Engine Finders UK Ltd. We are not affiliated with MERCEDES-BENZ or any other manufacturer. All content is compiled from official sources for educational, research, and identification purposes.
Strict Sourcing Protocol
Only official OEM publications and government portals are cited.
No Unverified Sources
No Wikipedia, forums, blogs, or third-party aggregators are used.
Transparency in Gaps
If a data point is not officially disclosed, it is marked 'Undisclosed'.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
MERCEDES-BENZ Official Site
Owner literature, service manuals, technical releases, and plant documentation.
EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
Type-approval guidance and documentation.
Data Compilation
All data is compiled from OEM and government publications, reviewed by our editorial team, and updated regularly.
Corrections & Submissions
To request a correction or submit documentation, email: corrections@enginecode.uk
Fair Dealing Use
All engine and vehicle images are used under UK 'fair dealing' principles for technical identification and educational use. Rights remain with their respective owners.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
GDPR Compliance
EngineCode.uk complies with UK GDPR. We do not collect personal data unless explicitly provided.
Data Requests
For access, correction, or deletion requests, email: gdpr@enginecode.uk
Trademark Notice
All trademarks, logos, and engine codes are the property of their respective owners. Use on this site is strictly for reference and identification.
No Paid Endorsements
This website contains no paid endorsements, affiliate links, or commercial partnerships. We do not sell parts or services.
Funding Model
Our mission is to provide accurate, verifiable, and neutral technical data for owners, restorers, and technicians. This site is self-funded.
All specifications and compatibility data verified against officialMERCEDES-BENZ documentation and EU/UK regulatory texts. Where official data is unavailable, entries are marked “Undisclosed“ .
All external links open in new tabs. Please verify current availability of resources.
