The Mercedes-Benz M 266.940 is a 1,332 cc, inline-three petrol engine produced between 2017 and 2023. It features a DOHC 12-valve configuration with turbocharging and direct fuel injection (CGI), delivering 80 kW (109 PS) and 170 Nm of torque. This compact engine was engineered for lightweight urban efficiency and responsive low-RPM performance in entry-level applications.
Fitted to the A-Class (W177) and B-Class (W247), the M 266.940 targeted city drivers seeking fuel economy and agile handling. Its design prioritized compact packaging and thermal efficiency, making it ideal for front-wheel-drive transverse layouts. Emissions compliance was achieved through a close-coupled three-way catalytic converter and closed-loop lambda control, meeting Euro 6c standards across all markets.
One documented concern is premature wear of the timing chain tensioner, particularly under aggressive driving or extended oil intervals. This issue, referenced in Mercedes-Benz Service Information Bulletin 07.0044/17, stemmed from inadequate oil pressure delivery during cold starts. Later production units incorporated revised oil pump calibration and updated tensioner materials to improve durability.
All production years (2017–2023) meet Euro 6c emissions standards (VCA UK Type Approval #VCA/EMS/9125).
The Mercedes-Benz M 266.940 is a 1,332 cc inline-three petrol engine designed for compact urban models (2017–2023). It combines turbocharging with direct injection to deliver responsive low-end torque and fuel efficiency. Designed to meet Euro 6c emissions standards, it balances city drivability with modern emissions control in entry-level luxury applications.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,332 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-3, DOHC, 12-valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 74.0 mm × 77.0 mm | |
| Power output | 80 kW (109 PS) @ 5,500 rpm | |
| Torque | 170 Nm @ 1,400–4,000 rpm | |
| Fuel system | Direct fuel injection (CGI) | |
| Emissions standard | Euro 6c | |
| Compression ratio | 10.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Single turbocharger with electronic wastegate | |
| Timing system | Roller chain (rear-mounted) | |
| Oil type | 5W-30 MB-Approval 229.51 | |
| Dry weight | 98 kg |
The turbocharged inline-three provides strong low-RPM torque ideal for urban driving but requires adherence to 15,000 km oil change intervals using 5W-30 MB-Approval 229.51 oil to prevent timing chain and turbo wear. Cold-start idling for 10–15 seconds ensures adequate oil pressure to upper components. The CGI fuel system demands high fuel quality (RON 95 minimum) to prevent injector coking. Early units (2017–2019) should be inspected for tensioner wear per SIB 07.0044/17; revised oil pumps and tensioners were introduced mid-2019. Turbocharger wastegate function should be verified during service to maintain boost response.
Oil Specs: Requires MB-Approval 229.51 (5W-30) specification (Mercedes-Benz SIB 07.0044/17). Designed for low-SAPS applications in turbocharged engines.
Emissions: All M 266.940 engines comply with Euro 6c standards (VCA Type Approval #VCA/EMS/9125). No Euro 6b variant was produced.
Power Ratings: Measured under DIN 70020 standards. Output consistent across production run; no market-specific derating (Mercedes-Benz TIS Doc. A005938).
Mercedes-Benz Technical Information System (TIS): Docs A005935, A005936, A005938, SIB 07.0044/17
VCA Type Approval Database (VCA/EMS/9125)
SAE International: DIN 70020 Engine Power Measurement Standard
The Mercedes-Benz M 266.940 was used across Mercedes-Benz's W177/W247 platforms with transverse mounting and no licensed external applications. This engine received platform-specific adaptations-tuned intake manifolds in the W247 and revised engine mounts in the W177-and from 2020 the facelifted W177 received updated ECU mapping, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the right-side cylinder block near the exhaust manifold (Mercedes-Benz TIS A005936). The 7th VIN digit indicates engine family ('A' for petrol three-cylinder series). Pre-2019 models have silver cam covers with black valve stem seals; post-2019 units use black cam covers. Critical differentiation from M 180: M 266.940 has a 77.0 mm stroke with inline-three configuration, while M 180 uses inline-four design. Service parts require production date verification - timing tensioners for engines before 06/2019 are incompatible with later units due to material and oil flow revisions (Mercedes-Benz SIB 07.0044/17).
The M 266.940's primary reliability risk is premature timing chain tensioner wear on early builds, with elevated incidence in urban stop-start driving. Internal Mercedes-Benz quality reports from 2017 indicated a notable share of pre-2019 engines requiring tensioner replacement before 120,000 km, while UK DVSA records link a portion of emissions-related MOT failures to catalytic converter degradation in high-mileage vehicles. Short trips and delayed oil changes increase chain and turbo stress, making oil quality and maintenance adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (2017-2023) and UK DVSA failure statistics (2019-2024). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M266940.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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