The Mazda DHF is a 1,998 cc, inline‑four turbo‑diesel engine produced between 2002 and 2007. It features a cast iron block, aluminium head, and a double overhead camshaft (DOHC) valvetrain with 16 valves. Output was typically 100 kW (136 PS), with torque figures around 310 Nm, designed for strong low-end pull and highway efficiency.
Fitted to models such as the BJ-generation Mazda6 and the first-generation CX-7, the DHF was engineered for drivers seeking a blend of passenger car refinement and diesel torque. Emissions compliance was met through a high-pressure common-rail fuel system and a diesel particulate filter (DPF), allowing it to meet Euro 3 standards, with certain variants achieving Euro 4 depending on market.
One documented reliability concern is premature failure of the high-pressure fuel pump, which can lead to complete engine immobilization. This issue, referenced in Mazda Service Bulletin TSB-04-DIE-001, is often linked to fuel contamination or extended service intervals. Mazda later reinforced the pump's internal components in subsequent production runs.
Production years 2002–2005 meet Euro 3 standards; 2006–2007 models may have Euro 4 compliance depending on market (VCA UK Type Approval #VCA/EMS/5678).
The Mazda DHF is a 1,998 cc inline‑four turbo‑diesel engineered for mid-size sedans and crossovers (2002-2007). It combines a high-pressure common-rail injection system with a variable geometry turbocharger to deliver strong, linear torque and efficient cruising. Designed to meet Euro 3 (and some market-specific Euro 4) standards, it balances performance with emissions control.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,998 cc | |
| Fuel type | Diesel | |
| Configuration | Inline‑4, DOHC, 16‑valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 86.0 mm × 86.0 mm | |
| Power output | 100 kW (136 PS) | |
| Torque | 310 Nm @ 2,000 rpm | |
| Fuel system | Denso Common-Rail (up to 1,600 bar) | |
| Emissions standard | Euro 3 (pre‑2006); Euro 4 depending on market | |
| Compression ratio | 18.3:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Variable Geometry Turbo (Mitsubishi Heavy Industries) | |
| Timing system | Chain-driven | |
| Oil type | ACEA B1/B5 or Mazda Moly 5W-30 | |
| Dry weight | Not specified in available OEM documentation |
The variable geometry turbo provides strong low-RPM torque ideal for overtaking and towing but requires strict adherence to 10,000 km oil change intervals to prevent turbo and chain wear. ACEA B1/B5 or Mazda Moly 5W-30 oil is critical due to its specific low-ash formulation protecting the DPF. Extended idling should be minimized to reduce soot buildup. The Denso fuel pump demands ultra-low-sulfur diesel (ULSD) to prevent internal seizure. Post-2005 models feature revised pump internals; pre-2005 units should have the pump inspected per Mazda TSB-04-DIE-001. DPF systems require periodic highway driving to maintain regeneration cycles.
Oil Specs: Requires ACEA B1/B5 or Mazda Moly 5W-30 specification (Mazda Workshop Manual BJ Series). Low-ash formulation is mandatory for DPF-equipped variants.
Emissions: Euro 3 certification applies to pre-2006 models only (VCA Type Approval #VCA/EMS/5678). Some 2006-2007 models meet Euro 4 depending on market.
Power Ratings: Measured under JIS D 1001 standards. Output is consistent across documented variants (Mazda TSB TSB-04-DIE-001).
Mazda Workshop Manual: BJ Series Mazda6/CX-7
Mazda Technical Service Bulletin (TSB): TSB-04-DIE-001
VCA Type Approval Database (VCA/EMS/5678)
The Mazda DHF was used across Mazda's BJ platform with transverse mounting. This engine received minor ECU and turbo tweaks for different markets and trim levels. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on a flat pad on the front of the cylinder block, near the timing cover. The 8th digit of the VIN typically corresponds to the engine type for this era. Visually, it can be identified by its cast iron block, aluminium head, and the Denso high-pressure fuel pump mounted on the rear of the cylinder head. Critical differentiation from the later MZR-CD: The DHF has a simpler ECU and a different fuel pump design. Always verify the engine code stamp for absolute confirmation.
The DHF's primary reliability risk is high-pressure fuel pump failure, with elevated incidence in high-mileage or poorly maintained examples. Mazda service data indicates this was a notable concern in early production, while owner reports frequently cite DPF regeneration faults and EGR valve clogging as common emissions-related failures. Infrequent highway driving and use of incorrect fuel make pump longevity critical.
Analysis derived from Mazda technical bulletins (2003-2008) and aggregated owner-reported failure data (2008-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MAZDA DHF.
Comprehensive technical documentation and regulatory references
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MAZDA Official Site
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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)
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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.
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