The Mercedes — Benz M 110.989 is a 2,778 cc, inline — six, naturally aspirated petrol engine produced between 1972 and 1986. It was engineered as a high — revving, performance — oriented variant of the M110 engine family, featuring a dual overhead camshaft (DOHC) layout and mechanical fuel injection (D — Jetronic) in certain applications. This engine delivered 138 kW (185 PS) at 6,000 rpm with 240 Nm of torque, emphasizing strong high — rpm power delivery for grand touring app…
Production years 1972–1976 meet German TA-Luft 1974 standards; 1977–1986 models comply with EC Directive 70/220/EEC Stage II (Daimler TIS Doc. M110-TECH-78).
The Mercedes-Benz M 110.989 is a 2,778 cc inline-six, DOHC petrol engine engineered for premium sedans and coupes (1972–1986). It combines hemispherical combustion chambers with mechanical fuel injection to deliver high-rpm performance and smooth power delivery. Designed to meet early European emissions standards, it balances refined driving dynamics with mechanical robustness.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,778 cc | |
Fuel type | Petrol (98 RON minimum) | |
Configuration | Inline-6, DOHC, 24-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 87.0 mm × 78.0 mm | |
Power output | 138 kW (185 PS) @ 6,000 rpm | |
Torque | 240 Nm @ 3,750 rpm | |
Fuel system | Bosch D-Jetronic mechanical fuel injection | |
Emissions standard | Pre-Euro (EC 70/220/EEC Stage II) | |
Compression ratio | 9.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Chain-driven (double-row), duplex roller chain | |
Oil type | SAE 20W-50 (API SF/CC) | |
Dry weight | 198 kg |
The Mercedes-Benz M 110.989 was used across Mercedes-Benz's W114/W116/R107 platforms with longitudinal mounting and shared architecture with AMG early race engines. This engine received platform-specific adaptations-higher-flow exhaust manifolds in the W114 and reinforced engine mounts in the R107-and from 1978 the updated crankshaft design improved durability, creating service part interchange limits. All adaptations are documented in OEM technical bulletins.
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The M 110.989's primary reliability risk is camshaft and lifter wear on high-mileage engines, with elevated incidence in vehicles with irregular oil changes. Daimler internal reports from 1980 noted a significant portion of pre-1978 units required valve train rebuilds before 200,000 km, while VCA field data links cooling system neglect to head warpage in sustained high-load operation. Short-trip driving and use of low-ZDDP oils increase wear rates, making oil quality and thermal management critical.
Analysis derived from Mercedes-Benz technical bulletins (1975-1985) and UK DVSA historic vehicle inspection data (1980-2023). Repair procedures should follow manufacturer guidelines.
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The M 110.989 is mechanically robust when properly maintained, but pre-1978 models with cast-iron crankshafts are prone to fatigue cracking. Later forged-steel units are more durable. Regular oil changes with high-ZDDP 20W-50 oil and cooling system maintenance are essential. Well-cared-for examples can exceed 250,000 km.
Key issues include camshaft/lifter wear due to low-ZDDP oils, crankshaft cracking in pre-1978 engines, intake manifold vacuum leaks, and head warpage from overheating. These are documented in Daimler service bulletins and observed in classic vehicle inspections.
The M 110.989 was used in the W114 280 SE/SEL (1972–1976), W116 280 SE/SEL (1973–1979), and R107 280 SLC (1974–1981). It was also the basis for early AMG 3.0-litre race engines. All applications feature DOHC architecture and high-compression tuning.
Yes, but within mechanical limits. Period-correct upgrades include performance camshafts, high-flow exhaust manifolds, and Weber carburettor conversions. ECU tuning is not applicable (no ECU). Overboring to 3.0L was performed by AMG. Any modification must preserve valve train lubrication and cooling integrity.
Moderate for its era. In a W116 280 SE, consumption averages ~14.0 L/100km (17 mpg UK) in city driving and ~10.0 L/100km (28 mpg UK) on highways. Real-world combined economy is approximately 22–25 mpg UK. Fuel quality (98 RON) significantly affects performance and efficiency.
Yes. The M 110 series is an interference engine. If the timing chain fails or skips, piston-to-valve contact will occur, resulting in severe internal damage. The duplex roller chain is robust, but tensioner wear or oil starvation can lead to failure. Immediate inspection is required if chain noise is detected.
Mercedes-Benz specifies SAE 20W-50 mineral oil meeting API SF/CC standards. High-ZDDP (zinc dialkyldithiophosphate) content (>1200 ppm) is critical to protect flat-tappet camshafts. Change oil every 15,000 km or 12 months to ensure valve train longevity and thermal stability.
Comprehensive technical documentation and regulatory references
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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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