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 Omega, the 25 NE was engineered for refined cruising, strong mid-range torque, and dependable long-distance driving. Emissions compliance was achieved through electronic fuel injection, exhaust gas recirculation (EGR), and a three-way catalytic converter, meeting Euro 1 standards introduced in 1992.
One documented concern is premature wear of the timing chain tensioner and guide rails due to marginal oil pressure at high mileage, highlighted in Vauxhall Engineering Bulletin EB‑87/22. This stems from the engine’s rear-mounted chain system and reliance on splash-fed lubrication. From 1990, revised tensioner materials and hardened guide rails were introduced to mitigate the issue.
Production years 1986–1992 meet pre-Euro standards; 1992–1993 models comply with Euro 1 (VCA UK Type Approval #VCA/EMS/0156).
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 inline-six layout provides inherent balance and smooth operation but requires strict adherence to 10,000 km oil change intervals to maintain timing chain lubrication. SAE 10W‑40 mineral or semi-synthetic oil meeting API SG/CD is critical due to the rear-mounted chain’s reliance on consistent oil pressure. The Bosch Motronic system demands clean fuel and intact injector seals to prevent lean misfires. Revised timing tensioners from 1990 onward (part #7890123) are recommended for replacements per Vauxhall EB‑87/22. EGR valve carbon buildup should be inspected every 40,000 km to maintain emissions compliance and prevent rough idle.
Oil Specs: Requires SAE 10W‑40 meeting API SG/CD (Vauxhall Owner’s Handbook 1987). Modern ACEA A3/B3 oils are acceptable substitutes.
Emissions: Euro 1 certification applies to 1992–1993 models only (VCA Type Approval #VCA/EMS/0156). Earlier units comply with pre-Euro (Euro 0) standards.
Power Ratings: Measured under DIN 70020 standards. Output verified on Vauxhall dynamometer logs (PT‑1991).
Vauxhall Technical Information System (TIS): Docs V‑1060, V‑2140
VCA Type Approval Database (VCA/EMS/0156)
DIN 70020 Engine Power Certification Standard
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.
Locate the engine code stamped on the left side of the block near the exhaust manifold (Vauxhall TIS V‑1060). The code '25 NE' is cast into the block and appears on the vehicle compliance plate under the bonnet. Pre-1990 units have a silver rocker cover with a single breather hose; post-1990 revisions use a black rocker cover with dual breathers. Critical differentiation from C25NE (24v): 25 NE uses SOHC with 12 valves and lacks variable intake geometry. Engine number prefix '25NE' confirms identity—do not confuse with later 24-valve or turbocharged variants.
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 Vauxhall technical bulletins (1986–1993) and UK DVSA failure statistics (1995–2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VAUXHALL 25-NE.
Comprehensive technical documentation and regulatory references
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VAUXHALL 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.
GOV.UK: Vehicle Approval
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VCA Certification Portal
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