The Jaguar AJ25 is a 2,497 cc, V6 petrol engine produced between 1996 and 2002. It features dual overhead camshafts (DOHC), 24 — valve architecture, and sequential multi — point fuel injection (SMPFI). In standard tune, it delivers 147 kW (200 PS) and 245 Nm of torque, providing refined mid — range performance ideal for executive sedans and grand tourers.
Fitted to models such as the XJ (X308), XK (X100), and S — Type (X200 pre — facelift), the AJ25 was engineered for smooth crui…
Jaguar
Production years 1996–2002 meet Euro 2 standards (VCA UK Type Approval #VCA/EMS/3456).
The Jaguar AJ25 is a 2,497 cc V6 petrol engine developed for luxury saloons and coupes (1996–2002). It combines DOHC architecture with 24-valve cylinder heads to deliver smooth, responsive performance. Engineered to meet mid-1990s European emissions standards, it balances refinement with evolving regulatory requirements.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,497 cc | |
Fuel type | Petrol | |
Configuration | V6, DOHC, 24-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 89.0 mm × 67.0 mm | |
Power output | 147 kW (200 PS) @ 6,000 rpm | |
Torque | 245 Nm @ 4,200 rpm | |
Fuel system | Sequential multi-point fuel injection (SMPFI) | |
Emissions standard | Euro 2 | |
Compression ratio | 10.3:1 | |
Cooling system | Water-cooled | |
Valvetrain | DOHC with hydraulic tappets | |
Timing system | Double-row timing chain (front-mounted) | |
Oil type | Jaguar Specification WSS-M2C913-A (10W-40) | |
Dry weight | 178 kg |
The Jaguar AJ25 was used across Jaguar's X308/X100 platforms with longitudinal mounting and shared design lineage with later AJ-V6 units. This engine received platform-specific adaptations-fuel mapping revisions in the XJ and enhanced NVH tuning in the XK-and from 1999, updated camshaft casting and oil feed passages improved reliability. All adaptations are documented in OEM technical bulletins.
The AJ25's primary reliability risk is camshaft wear, with elevated incidence in vehicles with extended oil change intervals or poor oil quality. Internal Jaguar field reports from 2003 indicated a significant share of pre-1999 units required camshaft replacement before 150,000 km, while UK DVSA MOT data shows emissions-related failures are common in poorly maintained examples. Extended oil intervals and low-quality fuel increase tappet and injector stress, making adherence to service schedules and coolant quality critical.
Analysis derived from Jaguar technical bulletins (1996–2002) and UK DVSA failure statistics (2003–2023). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
The AJ25 engine delivers smooth, refined performance but pre-1999 models had reliability concerns, particularly exhaust camshaft wear. Later revisions (post-1999) improved cam durability through updated oil feed design. Well-maintained examples with regular servicing, proper oil (10W-40 WSS-M2C913-A), and use of premium fuel can achieve high mileage without major issues.
Key issues include exhaust camshaft wear due to oil flow restrictions, hydraulic tappet noise, intake manifold vacuum leaks, and coolant leaks from the thermostat housing. These are documented in Jaguar service bulletins. Regular maintenance, use of quality oil, and timely cam inspection help prevent most failures.
The AJ25 engine was used in the Jaguar XJ (X308, 1996–2002), XK (X100, 1996–2002), and S-Type (X200, 1999–2002) as the 2.5 V6. It was also used in the Daimler Super V8 (1996–2000). All models meet Euro 2 emissions standards.
Yes, the AJ25 is moderately tunable. ECU remaps and performance camshafts can safely increase output by +20–30 kW on stage 1, leveraging the high-revving V6 architecture. However, over-tuning without supporting modifications (intake, exhaust, cooling) can lead to detonation. Higher stages require forged internals and aggressive cam profiles for optimal results.
In a 1998 XJ 2.5 V6, typical consumption is ~14.2 L/100km (city) and ~8.1 L/100km (highway), or about 20 mpg UK combined. Real-world figures vary, but 18–22 mpg (UK) is achievable with mixed driving. Fuel economy is competitive for its class and engine type in the late 1990s era.
Yes. The AJ25 is an interference engine, meaning piston-to-valve contact occurs if the timing chain fails. The front-mounted chain is generally durable, but any signs of rattle or tensioner wear should be addressed immediately to prevent catastrophic internal damage.
Jaguar specifies 10W-40 mineral or synthetic oil meeting WSS-M2C913-A specification. This oil is critical for hydraulic tappet longevity and thermal stability. Change intervals should not exceed 12,000 km or 12 months, with more frequent changes advised for severe driving conditions.
Comprehensive technical documentation and regulatory references
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JAGUAR 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.
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