The Vauxhall 25 NE is a 2,490 cc, inline‑six naturally aspirated petrol engine produced between 1986 and 1993. It features a single overhead camshaft (SOHC), two valves per cylinder, and multi — point fuel injection. In standard form it delivered 98 kW (133 PS) at 5,200 rpm and 205 Nm of torque at 3,200 rpm, offering smooth power delivery suited to executive saloons and performance variants of the era.
Fitted to models such as the Carlton Mk2 (Omega A), Senator B, and Vauxhall O…
Production years 1986–1992 meet pre-Euro standards; 1992–1993 models comply with Euro 1 .
The Vauxhall 25 NE is a 2,490 cc inline‑six naturally aspirated petrol engine engineered for executive saloons and performance variants (1986–1993). It combines multi-point fuel injection with SOHC valvetrain to deliver smooth power delivery and predictable throttle response. Designed to meet Euro 1 emissions standards from 1992 onward, it balances refinement with mechanical simplicity.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,490 cc | |
Fuel type | Petrol (Unleaded, min. 95 RON) | |
Configuration | Inline‑6, SOHC, 12‑valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 88.0 mm × 68.5 mm | |
Power output | 98 kW (133 PS) @ 5,200 rpm | |
Torque | 205 Nm @ 3,200 rpm | |
Fuel system | Bosch Motronic MPFI (multi-point fuel injection) | |
Emissions standard | Pre-Euro (1986–1991); Euro 1 (1992–1993) | |
Compression ratio | 9.0:1 | |
Cooling system | Water‑cooled | |
Turbocharger | None | |
Timing system | Chain-driven SOHC (rear-mounted) | |
Oil type | SAE 10W‑40 (API SG/CD) | |
Dry weight | 142 kg |
The Vauxhall 25 NE was used across Vauxhall's Omega platform with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—reinforced engine mounts in the Senator B and modified intake manifolds in the Carlton GSi—and from 1990 the Omega facelift introduced updated timing components, creating minor service part distinctions. All adaptations are documented in OEM technical bulletins.
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The 25 NE's primary reliability risk is timing chain tensioner and guide wear, with elevated incidence in high-mileage or infrequently serviced engines. Vauxhall internal data from 1992 indicated timing-related repairs in approximately 12% of units exceeding 140,000 km without oil changes, while UK DVLA records show EGR-related drivability complaints as the second-most frequent advisory for this era. Infrequent oil changes and incorrect oil viscosity make proper maintenance critical.
Analysis derived from manufacturer technical service bulletins and industry workshop records. 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 25 NE is mechanically smooth and can be reliable if maintained properly. Early timing tensioner wear was an issue, addressed in 1990 revisions. Regular oil changes every 10,000 km, EGR cleaning, and fuel system maintenance are essential for longevity beyond 150,000 km.
Top issues include timing chain tensioner wear, EGR carbon buildup causing rough idle, fuel injector leaks, and oil leaks from aged gaskets. These are documented in Vauxhall Engineering Bulletin EB‑87/22 and service manuals.
The 25 NE powered the Carlton Mk2 (1986–1993), Senator B (1987–1993), and Omega A (1986–1993) in 2.5i form. It was exclusive to Vauxhall/Opel and not used by other manufacturers.
Modest gains are possible. Upgrading to a performance exhaust, high-flow air filter, and ECU remap can yield +10–15 PS. However, the SOHC 12-valve head limits airflow—significant tuning is not recommended without head work.
Typical consumption is ~11.0 L/100km (city) and ~7.5 L/100km (highway), or about 24 mpg UK combined. Real-world figures range from 22–27 mpg UK depending on condition and driving style.
Yes. The 25 NE is an interference engine. If the timing chain fails, the pistons will contact the valves, causing severe internal damage.
Vauxhall specifies SAE 10W‑40 mineral or semi-synthetic oil meeting API SG/CD. Change every 10,000 km or 12 months. Modern ACEA A3/B3 oils are acceptable substitutes.
Comprehensive technical documentation and regulatory references
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Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
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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