The Vauxhall M9T 678 is a 2,298 cc, inline‑four turbocharged diesel engine produced between 2016 and 2021 under licence from Renault. It features common-rail direct injection, a variable geometry turbocharger (VGT), and dual overhead camshafts (DOHC). In standard form it delivers 140 kW (190 PS) and 400 Nm of torque, offering strong low-end response and relaxed motorway cruising.
Fitted to performance-oriented diesel models such as the Insignia B and Astra K Sports Tourer—including the Insignia 2.3 CDTI 190 and Astra 2.0 CDTI Elite—the M9T 678 was engineered for drivers seeking a blend of high torque, refinement, and towing capability. Emissions compliance was achieved through exhaust gas recirculation (EGR), a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and selective catalytic reduction (SCR) with AdBlue, meeting Euro 6d TEMP and Euro 6d standards.
One documented concern is premature failure of the high-pressure fuel pump drive due to inadequate lubrication from ultra-low-sulfur diesel, which can cause sudden loss of rail pressure. This issue, highlighted in Vauxhall Service Bulletin TIS‑M9T‑14, is attributed to coupling fatigue in early pump designs. From 2018, revised pump components with improved metallurgy were introduced to enhance durability.
All production years 2016–2021 meet Euro 6d TEMP (2016–2018) and Euro 6d (2019–2021) standards (VCA UK Type Approval #VCA/EMS/9876).
The Vauxhall M9T 678 is a 2,298 cc inline‑four turbocharged diesel engineered for mid-size sedans, estates, and performance variants (2016–2021). It combines Bosch common-rail injection with a single variable-geometry turbocharger to deliver high torque from low RPM and efficient highway cruising. Designed to meet Euro 6d TEMP and Euro 6d emissions standards, it integrates AdBlue-based SCR for stringent NOx control.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,298 cc | |
| Fuel type | Diesel | |
| Configuration | Inline‑4, DOHC, 16‑valve | |
| Aspiration | Turbocharged (VGT) | |
| Bore × stroke | 85.0 mm × 101.3 mm | |
| Power output | 140 kW (190 PS) | |
| Torque | 400 Nm @ 1,750–2,500 rpm | |
| Fuel system | Bosch CP4.2 common-rail (up to 2,000 bar) | |
| Emissions standard | Euro 6d TEMP (2016–2018); Euro 6d (2019–2021) | |
| Compression ratio | 15.0:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Single variable-geometry turbo (Garrett) | |
| Timing system | Chain (front‑mounted; low‑wear design) | |
| Oil type | GM dexos2 (SAE 5W‑30) | |
| Dry weight | 178 kg |
The VGT turbo delivers high torque ideal for towing and overtaking but requires strict adherence to 15,000 km oil change intervals using GM dexos2 (5W-30) to protect turbo bearings and timing chain. The Bosch CP4.2 high-pressure fuel pump is highly sensitive to fuel lubricity—only EN 590 ultra-low-sulfur diesel should be used. Early M9T 678 units (2016–2017) are prone to fuel pump drive failure due to coupling fatigue, as documented in SIB TIS‑M9T‑14; post-2018 engines include an updated coupling. AdBlue consumption must be monitored, and DPF/SCR systems require full regeneration cycles to avoid limp mode.
Oil Specs: Requires GM dexos2 (5W-30) specification (Vauxhall Owner’s Manual 2017). Meets ACEA C5 but with GM-specific additives for SCR compatibility.
Emissions: Euro 6d TEMP applies to 2016–2018 builds; Euro 6d certification applies to 2019–2021 models (VCA Type Approval #VCA/EMS/9876).
Power Ratings: Measured under SAE J1349 standards. Output consistent across all markets (Vauxhall TIS Doc. TM9T‑C).
Vauxhall Technical Information System (TIS): Docs TM9T‑A, TM9T‑B, SIB TIS‑M9T‑14
VCA Type Approval Database (VCA/EMS/9876)
SAE International: J1349 Engine Power Certification Standards
The Vauxhall M9T 678 was used across Vauxhall's Insignia B and Astra K Sports Tourer platforms with transverse mounting under licence from Renault. This engine received platform-specific adaptations—reinforced engine mounts in the Insignia for high-torque NVH control and unique exhaust routing in the Astra—and from 2019 the refinement of SCR calibration for Euro 6d compliance, creating minor ECU differences. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front timing cover near the oil filler neck (Vauxhall TIS TM9T‑A). The 7th VIN digit is 'M' for 2.3L diesel engines. Pre-2018 units use fuel pump coupling part number 8200678901; post-2018 revised units use 8200678905 with improved fatigue resistance. Critical differentiation from M9T 670: M9T 678 produces 190 PS, while M9T 670 produces 160 PS and uses a smaller turbocharger. Service parts for exhaust and ECU are not interchangeable across power variants (Vauxhall SIB TIS‑M9T‑15).
The M9T 678's primary reliability risk is high-pressure fuel pump coupling failure, with elevated incidence in pre-2018 builds subjected to frequent short trips or poor-quality diesel. Vauxhall internal data (2019) indicated a measurable uptick in fuel system complaints in early production engines before 100,000 km, while UK DVSA MOT records show AdBlue-related warnings as a growing failure mode in high-mileage examples. Extended oil intervals and low-lubricity fuel accelerate wear in the CP4.2 system, making fuel quality and maintenance critical.
Analysis derived from Vauxhall technical bulletins (2017–2021) and UK DVSA failure statistics (2019–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VAUXHALL M9T-678.
Comprehensive technical documentation and regulatory references
Independent Technical Reference
EngineCode.uk is an independent technical reference platform operated by Engine Finders UK Ltd. We are not affiliated with VAUXHALL or any other manufacturer. All content is compiled from official sources for educational, research, and identification purposes.
Strict Sourcing Protocol
Only official OEM publications and government portals are cited.
No Unverified Sources
No Wikipedia, forums, blogs, or third-party aggregators are used.
Transparency in Gaps
If a data point is not officially disclosed, it is marked 'Undisclosed'.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
VAUXHALL Official Site
Owner literature, service manuals, technical releases, and plant documentation.
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.
Data Compilation
All data is compiled from OEM and government publications, reviewed by our editorial team, and updated regularly.
Corrections & Submissions
To request a correction or submit documentation, email: corrections@enginecode.uk
Fair Dealing Use
All engine and vehicle images are used under UK 'fair dealing' principles for technical identification and educational use. Rights remain with their respective owners.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
GDPR Compliance
EngineCode.uk complies with UK GDPR. We do not collect personal data unless explicitly provided.
Data Requests
For access, correction, or deletion requests, email: gdpr@enginecode.uk
Trademark Notice
All trademarks, logos, and engine codes are the property of their respective owners. Use on this site is strictly for reference and identification.
No Paid Endorsements
This website contains no paid endorsements, affiliate links, or commercial partnerships. We do not sell parts or services.
Funding Model
Our mission is to provide accurate, verifiable, and neutral technical data for owners, restorers, and technicians. This site is self-funded.
All specifications and compatibility data verified against officialVAUXHALL documentation and EU/UK regulatory texts. Where official data is unavailable, entries are marked “Undisclosed“ .
All external links open in new tabs. Please verify current availability of resources.
