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 primari…
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 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.
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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.
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The M115.972 is mechanically robust when properly maintained. Early models (1968-1971) had timing chain tensioner issues, but post-1972 revisions improved durability. Regular oil changes with SAE 20W-50, carburettor servicing, and cooling system maintenance are essential. Well-kept examples can exceed 200,000 km with minimal issues.
Key issues include timing chain tensioner wear (especially pre-1972), carburettor imbalance due to worn Solex units, cooling system leaks, and hydraulic tappet noise. These are documented in Mercedes-Benz service literature and addressed through OEM-recommended updates and maintenance procedures.
The M115.972 was used in the W114 280 and W114 280C (1968–1976) and the W115 280 (1968–1976). It was not used in coupes or convertibles outside of the W114 platform. No cross-manufacturer applications exist for this variant.
Limited tuning potential exists. Performance upgrades include high-flow air filters, tuned exhaust manifolds, and modified camshafts. Carburettor swaps (e.g., triple Webers) are possible but require custom manifolds. ECU tuning is not applicable—ignition is distributor-based. Realistic gains are +15–25 PS with supporting modifications.
Factory figures indicate ~13.5 L/100km (21.0 mpg UK) in combined driving. Real-world consumption ranges from 12.0–15.0 L/100km (19–24 mpg UK) depending on driving style and vehicle condition. Carburettor tune and tyre pressure significantly affect efficiency.
No. The M115.972 is a non-interference engine. If the timing chain fails, piston-to-valve contact is unlikely, reducing risk of catastrophic internal damage. However, immediate repair is still advised to prevent secondary damage from incorrect valve timing.
Mercedes-Benz specifies SAE 20W-50 mineral oil meeting API SF/CC standards. Modern synthetic blends with equivalent viscosity are acceptable if compatible with vintage engine materials. Change intervals should not exceed 15,000 km or annually to ensure optimal lubrication of the timing chain and hydraulic tappets.
Comprehensive technical documentation and regulatory references
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Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
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.
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