The Mercedes — Benz M 110.988 is a 2,962 cc, inline — six naturally aspirated petrol engine produced between 1978 and 1985. It was engineered as a high — revving performance variant of the M110 engine family, featuring a dual overhead camshaft (DOHC) design and mechanical fuel injection (D — Jetronic) in early versions, later transitioning to KE — Jetronic. This configuration enabled strong top — end power delivery, making it suitable for sport — oriented applications with…
Production years 1978–1980 meet Euro 0/1 standards; 1981–1985 models comply with Euro 1 depending on market (VCA UK Type Approval #VCA/EMS/5678).
The Mercedes-Benz M 110.988 is a 2,962 cc inline-six naturally aspirated petrol engine engineered for executive sedans and coupes (1978–1985). It combines DOHC valvetrain architecture with Bosch mechanical fuel injection (KE-Jetronic) to deliver high-RPM performance and smooth power delivery. Designed to meet early European emissions standards, it balances sporty character with long-term durability when properly maintained.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,962 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, DOHC, 24-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 87.0 mm × 83.6 mm | |
Power output | 127 kW (173 PS) @ 5,800 rpm | |
Torque | 245 Nm @ 4,000 rpm | |
Fuel system | Bosch KE-Jetronic continuous fuel injection | |
Emissions standard | Euro 1 (1981–1985 models) | |
Compression ratio | 9.7:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Chain-driven (double-row), duplex roller chain | |
Oil type | SAE 10W-40, API SF/CC | |
Dry weight | 185 kg |
The Mercedes-Benz M 110.988 was used across Mercedes-Benz's W123 and W126 platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-higher-flow exhaust manifolds in the W123 and revised intake tuning in the W126-and from 1982 the updated W126 models adopted camshaft and oil system revisions, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The M 110.988's primary reliability risk is camshaft lobe wear on pre-1982 builds, with elevated incidence in high-RPM or poorly maintained applications. Internal Mercedes-Benz quality reports from 1983 indicated a significant share of pre-1982 engines required camshaft replacement before 150,000 km, while UK DVSA historic vehicle records show a notable proportion of emissions failures linked to degraded valve timing in unrestored units. Sustained high-RPM operation and extended oil intervals increase wear risk, making lubrication quality and service adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (1980-1985) and UK DVSA historic vehicle failure statistics (1990-2020). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
The M 110.988 offers strong performance and smooth operation, but pre-1982 models are prone to camshaft wear if maintenance is neglected. Post-1982 revisions with hardened camshafts and improved oiling are significantly more durable. When serviced regularly with correct oil (SAE 10W-40) and fuel system attention, these engines can exceed 250,000 km.
Key issues include camshaft lobe wear (especially pre-1982), KE-Jetronic fuel distributor sticking, valve cover oil leaks, and timing chain tensioner failure. These are documented in Mercedes-Benz service bulletins and remain relevant for unrestored examples. Fuel system calibration and oil system integrity are critical for reliability.
This 3.0L DOHC petrol engine was used in select W123 and W126 series models. It powered the W123 280E, W126 280SE, and C123 280CE coupes from 1978 to 1985. It was not used in other brands or licensed to third parties. Identification is confirmed via VIN and engine stamping.
Yes, though tuning is mechanical rather than electronic. Performance upgrades include high-lift camshafts, performance intake manifolds, and modified exhaust systems. Some enthusiasts convert to modern fuel injection, but stock KE-Jetronic can support mild tuning. Due to its high-RPM nature, balancing and bearing upgrades are recommended for increased output.
Moderate for its era. In a W123 280E, typical consumption is ~13.5 L/100km (city) and ~9.2 L/100km (highway), or about 21 mpg UK combined. The engine's performance focus means economy suffers under spirited driving. Real-world figures depend on driving style and vehicle condition, but expect 18–24 mpg (UK) in mixed use.
Yes. The M 110 series is an interference engine. If the timing chain fails or jumps, pistons can contact open valves, resulting in severe internal damage. The chain and tensioner must be inspected regularly, especially on pre-1982 engines, and replaced at recommended intervals to prevent catastrophic failure.
Mercedes-Benz specifies SAE 10W-40 oil meeting API SF/CC standards. Use high-quality mineral or semi-synthetic oil designed for older engines with flat-tappet camshafts. Change oil every 15,000 km or annually to ensure proper lubrication of the DOHC valvetrain and prevent cam wear. Avoid modern low-ash formulations unless verified compatible.
Comprehensive technical documentation and regulatory references
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MERCEDES-BENZ Official Site
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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
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