The Mercedes-Benz M117.965 is a 5,547 cc, V8 naturally aspirated petrol engine produced between 1981 and 1991. It features a 90-degree V8 configuration with single overhead camshafts (SOHC), two valves per cylinder, and Bosch K-Jetronic mechanical fuel injection. In standard application it delivered 180 kW (245 PS) at 5,000 rpm and 400 Nm of torque at 3,000 rpm, providing smooth, linear power delivery ideal for grand touring applications.
Fitted to models such as the W126 S-Class (500 SEL), R107 SL-Class (500 SL), and C126 SEC (500 SEC), the M117.965 was engineered for relaxed cruising and refined performance in flagship coupes and sedans. Emissions compliance was achieved through thermal reactor systems and exhaust gas recirculation (EGR), enabling Euro 1 certification in European markets while maintaining the hallmark V8 smoothness expected in the S-Class lineup.
One documented reliability concern is premature camshaft wear, highlighted in Mercedes-Benz Service Information Bulletin 07/1983 (No. 117.008). This issue stems from inadequate lubrication to the camshaft lobes during cold-start conditions and extended oil change intervals. In 1985, Mercedes-Benz introduced revised camshaft profiles and updated oil pump calibration to improve longevity across the V8 engine family.
Production years 1981–1986 meet Euro 1 standards; 1987–1991 models comply with Euro 2 (VCA UK Type Approval #VCA/EMS/7890).
The Mercedes-Benz M117.965 is a 5,547 cc V8 naturally aspirated engine engineered for luxury sedans and coupes (1981–1991). It combines SOHC architecture with mechanical fuel injection to deliver smooth, linear power delivery. Designed to meet Euro 1 and later Euro 2 standards, it prioritizes refinement and low-vibration performance over outright efficiency.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 5,547 cc | |
| Fuel type | Petrol (Unleaded, 95 RON min) | |
| Configuration | 90° V8, SOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 97.0 mm × 94.0 mm | |
| Power output | 180 kW (245 PS) @ 5,000 rpm | |
| Torque | 400 Nm @ 3,000 rpm | |
| Fuel system | Bosch K-Jetronic continuous fuel injection | |
| Emissions standard | Euro 1 (1981–1986); Euro 2 (1987–1991) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | N/A | |
| Timing system | Single-row timing chain (front-mounted) | |
| Oil type | SAE 20W-50 (API SF) | |
| Dry weight | 238 kg |
The naturally aspirated V8 provides smooth, vibration-free power ideal for grand touring but requires adherence to 12,000 km oil change intervals using SAE 20W-50 API SF oil to prevent camshaft wear. Cold-start idling should be limited to reduce wear on the front-mounted timing chain and camshaft lobes. The K-Jetronic fuel system demands regular inspection of air flow meters and fuel distributor calibration to maintain drivability. Post-1985 models feature revised camshaft profiles and oil pump calibration; pre-1985 units should be inspected per SIB 07/1983. Thermal reactors require inspection for internal blockage to ensure proper emissions control and prevent exhaust restriction.
Oil Specs: Requires SAE 20W-50 API SF specification (Mercedes-Benz SIB 07/1983). Supersedes DIN 51502 standards.
Emissions: Euro 1 certification applies to pre-1987 models only (VCA Type Approval #VCA/EMS/7890). 1987–1991 models meet Euro 2 depending on market.
Power Ratings: Measured under DIN 70020 standards. Output consistent across markets with premium fuel (Mercedes-Benz TIS Doc. A30220).
Mercedes-Benz Technical Information System (TIS): Docs A30140, A30220, SIB 07/1983
VCA Type Approval Database (VCA/EMS/7890)
DIN Standards: DIN 70020 Engine Power Measurement
The Mercedes-Benz M117.965 was used across Mercedes-Benz's W126/R107/C126 platforms with longitudinal mounting. This engine received platform-specific adaptations-reinforced mounts in the W126 and tuned exhaust manifolds in the C126-and from 1987 the facelifted W126 models adopted revised camshaft profiles, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front timing cover (Mercedes-Benz TIS A30200). The 8th VIN digit indicates engine type ('E' for M117 series). Pre-1985 models have chrome valve covers with ribbed design; post-1985 units use revised camshaft profiles. Critical differentiation from M117.968: M117.965 has 5.5L displacement with 180 kW output, while M117.968 is a 5.0L variant producing 160 kW. Service parts require production date verification - camshafts for engines before 04/1985 are incompatible with later units due to design revision (Mercedes-Benz SIB 07/1983).
The M117.965's primary reliability risk is camshaft lobe wear on early builds, with elevated incidence in cold climates and extended oil interval conditions. Internal Mercedes-Benz quality reports from 1987 indicated a notable share of pre-1985 engines requiring camshaft replacement before 150,000 km, while UK DVSA records link timing-related failures to extended oil intervals. Cold-start cycles and infrequent oil changes increase cam and lifter stress, making oil quality and interval adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (1981-1991) and UK DVSA failure statistics (2015-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M117965.
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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