The Mazda PEX3 is a 2,488 cc, inline‑four naturally aspirated petrol engine produced between 2019 and 2023. It features dual overhead camshafts (DOHC), 16 valves, and incorporates Mazda's advanced SKYACTIV — G technology with a high compression ratio for improved efficiency. In standard form, it produced 138 kW (188 PS) and 252 Nm of torque, offering a refined and linear power delivery suitable for larger SUV applications.
Fitted exclusively to the second — generation M…
Mazda
Production years 2019–2023 meet Euro 6d standards for all markets .
The Mazda PEX3 is a 2,488 cc inline‑four naturally aspirated petrol engine engineered for mid-size SUVs (2019-2023). It combines DOHC 16-valve architecture with direct injection and a high 13.0:1 compression ratio to deliver smooth, linear power and strong mid-range torque. Designed to meet Euro 6d standards, it prioritizes refinement and efficiency in larger vehicle applications.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,488 cc | |
Fuel type | Petrol | |
Configuration | Inline‑4, DOHC, 16‑valve | |
Aspiration | Naturally Aspirated | |
Bore × stroke | 89.0 mm × 100.0 mm | |
Power output | 138 kW (188 PS) @ 6,000 rpm | |
Torque | 252 Nm @ 4,000 rpm | |
Fuel system | Direct Injection (DI) | |
Emissions standard | Euro 6d | |
Compression ratio | 13.0:1 | |
Cooling system | Water‑cooled | |
Turbocharger | None | |
Timing system | Chain-driven | |
Oil type | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 156 kg |
The Mazda PEX3 was used across Mazda's KF and PY platforms with transverse mounting. This engine received a significant update in 2021 with the introduction of cylinder deactivation (CDA) technology on certain variants, which introduced new ECU software and valve train components, creating a clear distinction between pre- and post-2021 models. All adaptations are documented in OEM technical bulletins.
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Field reports and technical service bulletins highlight component wear patterns under high-load operation. Adherence to manufacturer service intervals and approved fluid specifications is critical for long-term reliability.
Analysis derived from manufacturer technical service bulletins and industry workshop records. Repair procedures should follow manufacturer guidelines.
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The PEX3 is considered a very reliable and robust engine. Its main considerations are typical GDI carbon buildup and, for 2021+ models, the complexity of the CDA system. With regular maintenance, using the correct 0W-20 oil, and quality fuel, it offers excellent long-term durability. The timing chain is designed for the engine's life.
The most frequently reported issues are carbon buildup on intake valves (common to all GDI engines), VVT solenoid malfunctions, worn engine mounts, and CDA system faults on 2021+ models. These are well-documented in Mazda service bulletins and owner reports.
The PEX3 2.5L Skyactiv-G petrol engine was used in the second-generation Mazda CX-5 (KF chassis, 2019-2023) and the first-generation Mazda CX-50 (PY chassis, 2022-2023). It was the standard non-turbo petrol engine for these SUVs in many global markets.
Gains are very limited due to its high compression and naturally aspirated design. A remap might yield 8-12 kW, but risks engine knock. Most 'tuning' focuses on throttle response. Significant power increases require forced induction, which is not a common or supported modification for this engine.
Fuel economy is respectable for a 2.5L engine in an SUV. Expect around 8.5 L/100km combined for a CX-5, translating to roughly 33 mpg (UK). CDA-equipped models may see a 5-10% improvement on highway cycles. Real-world figures depend heavily on driving style and vehicle load.
Yes. The PEX3 is an interference engine. If the timing chain were to fail (an extremely rare event), the pistons would collide with the open valves, causing catastrophic internal engine damage. This highlights the importance of using the correct oil to ensure chain lubrication.
Mazda specifies SAE 0W-20 engine oil meeting API SP or ILSAC GF-6 standards. Using a high-quality full synthetic 0W-20 oil is strongly recommended to protect the VVT system, ensure proper CDA operation (if equipped), and maintain the longevity of the timing chain.
Comprehensive technical documentation and regulatory references
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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
Type-approval guidance and documentation.
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