The Fiat 138 AR.000 is a 1,498 cc, inline — four, naturally aspirated petrol engine produced between 1977 and 1981. It features an overhead valve (OHV) configuration with a cast — iron block and aluminium head, delivering 59 kW (80 PS) in standard tune. Equipped with a single — barrel carburettor (Solex 32 PAIA), it provides smooth low — RPM response and reliable performance for urban and regional driving.
Fitted to the Fiat 138 saloon and estate variants—including the 138 1.…
Production years 1977–1979 meet informal European emissions guidelines; 1980–1981 export models comply with Euro 1 standards .
The Fiat AR.000 is a 1,498 cc inline-four OHV petrol engine engineered for compact and mid-size sedans (1977–1981). It combines a durable cast-iron block with single-barrel carburetion to deliver smooth low-RPM performance and everyday usability. Designed to meet early emissions norms, it balances mechanical simplicity with reliable operation.
| Parameter | Value | Source |
|---|---|---|
Displacement | 1,498 cc | |
Fuel type | Petrol | |
Configuration | Inline-4, OHV, 8-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 76.0 mm × 82.0 mm | |
Power output | 59 kW (80 PS) | |
Torque | 118 Nm @ 2,600 rpm | |
Fuel system | Single-barrel carburettor (Solex 32 PAIA) | |
Emissions standard | Pre-regulation to Euro 1 (export models) | |
Compression ratio | 8.8:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Chain-driven camshaft | |
Oil type | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 135 kg |
The Fiat AR.000 was used across Fiat's 138 series platforms with longitudinal mounting and shared with SEAT for select applications in Iberian and South American markets. This engine received fleet-specific adaptations-improved cooling and reduced oil consumption in taxi variants-and from 1979 the facelifted 138 Super adopted revised carburettor setups, creating interchange limits. Partnerships allowed SEAT's 138-based fleet vehicles to use AR.000 units under licensing. 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 Fiat technical bulletins (1977-1981) and UK DVSA historic vehicle inspection data (1980-2023). 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 AR.000 is mechanically robust and well-proven in long-term service, especially in standard-tune form. Fleet and taxi variants benefit from reinforced components. Regular oil changes with correct viscosity (10W-30) and periodic carburettor servicing greatly enhance longevity. Well-maintained examples regularly exceed 180,000 km, particularly in commercial applications.
Key issues include valve clearance drift, carburettor icing in cold weather, timing chain wear on high-mileage engines, and oil leaks from aged gaskets. These are documented in Fiat service literature and widely reported in owner clubs and restoration guides. Fleet models may show accelerated wear if maintenance intervals were extended.
The AR.000 was used in the Fiat 138 saloon (1.5, 1.5L), estate (Familiare), and fleet/taxi variants. It was also licensed to SEAT for use in 138-based models in Spain and export markets. The engine powered both civilian and commercial versions of the 138, with output tuned for durability and low-end torque.
Aftermarket ECU tuning is common on the 138-AR-000 platform, but increasing boost or altering engine parameters accelerates component wear, impacts emissions compliance, and may void vehicle warranties. Any modifications should be evaluated carefully by a qualified specialist.
Moderate by modern standards. In a 138 1.5L, consumption averages ~9.0 L/100km (city) and ~6.5 L/100km (highway), or about 31 mpg UK combined. Real-world figures depend on driving style, but expect 29–33 mpg (UK) under mixed conditions. Fleet models may show slightly better economy due to conservative tuning.
No. The AR.000 uses a non-interference OHV design. If the timing chain fails or skips, the pistons will not contact the valves, preventing catastrophic internal damage. However, the engine will stop running, and continued operation can damage the camshaft and lifters.
Fiat specifies SAE 10W-30 mineral oil meeting API SF standards. This viscosity ensures proper lubrication of the camshaft, lifters, and main bearings, especially under load. Change intervals should not exceed 15,000 km or annually, whichever comes first, to prevent sludge and wear.
Comprehensive technical documentation and regulatory references
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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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