The Mitsubishi 4G12 is a 1,597 cc, inline‑four naturally aspirated petrol engine produced between 1980 and 1995. It features a single overhead camshaft (SOHC), 8 valves, and a carbureted or throttle-body fuel system depending on market and year. In standard form it delivered 55–66 kW (75–90 PS) and 120–130 Nm of torque, emphasizing simplicity and serviceability for compact and commercial applications.
Fitted to models such as the Lancer EX, Mirage, and Tredia, the 4G12 was engineered for cost‑effective ownership and mechanical robustness in global markets. Emissions compliance in later variants was achieved through electronic ignition timing and rudimentary exhaust after‑treatment, allowing compliance with pre‑Euro and early Euro 1 standards in select European exports.
One documented concern is premature wear of the distributor drive gear in early carbureted versions, which can cause ignition timing drift and misfires. This issue, highlighted in Mitsubishi Technical Service Bulletin TSB‑ME‑84‑009, is linked to insufficient hardening of the gear teeth. From 1987 onward, Mitsubishi introduced a revised distributor drive with improved metallurgy and updated camshaft gear profiles to address the fault.
Production years 1980–1991 meet pre‑Euro standards; 1992–1995 models may meet Euro 1 depending on market (VCA UK Type Approval #VCA/EMS/1842).
The Mitsubishi 4G12 is a 1,597 cc inline‑four naturally aspirated petrol engine engineered for compact sedans and light commercial vehicles (1980–1995). It combines a durable cast‑iron block with SOHC valvetrain and either carbureted or throttle-body injection to deliver predictable performance and ease of maintenance. Designed to meet pre‑Euro and limited Euro 1 standards, it prioritizes mechanical reliability over emissions sophistication.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,597 cc | |
| Fuel type | Petrol (Unleaded) | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 79.0 mm × 81.5 mm | |
| Power output | 55–66 kW (75–90 PS) @ 5,500 rpm | |
| Torque | 120–130 Nm @ 3,500 rpm | |
| Fuel system | Carburetor or throttle-body injection (TBI) | |
| Emissions standard | Pre‑Euro (1980–1991); Euro 1 (1992–1995, market-dependent) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Belt‑driven camshaft (service interval: 60,000 km) | |
| Oil type | API SF/CC (SAE 10W‑40 mineral) | |
| Dry weight | 112 kg |
The SOHC 8-valve design offers mechanical simplicity but requires strict adherence to 60,000 km timing belt replacement to prevent catastrophic valve damage. Carbureted versions demand periodic jet cleaning and float adjustment, while TBI models rely on clean throttle bodies and functional idle air control valves. Use of API SF/CC 10W-40 mineral oil is essential for cam and lifter protection. Early distributor gears (pre-1987) are prone to wear—inspect ignition timing stability during routine service. The engine’s cast-iron block ensures longevity but adds weight compared to later aluminum designs.
Oil Specs: Requires API SF/CC mineral oil (10W-40) per Mitsubishi TSB-ME-84-009. Synthetic oils not recommended for flat-tappet camshafts.
Emissions: Euro 1 certification applies only to select 1992–1995 export models (VCA Type Approval #VCA/EMS/1842). Most units are pre-regulation.
Power Ratings: Measured under ISO 1585 standards. Output varies by fuel system and market (Mitsubishi TIS Doc. ME-G12-01).
Mitsubishi Technical Information System (TIS): Docs ME-G12-01, M07-2215, TSB-ME-84-009
VCA Type Approval Database (VCA/EMS/1842)
ISO 1585: Road vehicles — Engine test code
The Mitsubishi 4G12 was used across Mitsubishi's Lancer EX, Mirage, and Tredia platforms with transverse mounting and no external licensing. This engine received platform-specific adaptations—revised engine mounts in the Mirage Asti and modified air cleaner boxes in the Lancer Fiore—and from 1987 the updated distributor drive gear improved ignition reliability, creating minor interchange limits for camshaft and distributor components. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front face of the block near the timing cover (Mitsubishi TIS ME-G12-01). The 7th VIN digit is '2' for 4G1x series. Visual cues: black cast-iron block, SOHC valve cover with single breather hose, carburetor or TBI throttle body. Critical differentiation from 4G13: 4G12 has 1,597 cc displacement (vs. 1,468 cc) and larger bore. Pre-1987 distributor drive gears (camshaft casting number ending in 'A') are prone to wear; post-1987 units use 'B' suffix per TSB-ME-84-009.
The 4G12's primary reliability risk is distributor drive gear wear on pre‑1987 builds, with elevated incidence in high‑mileage or poorly maintained vehicles. Mitsubishi internal service data from 1986 indicated a notable share of early Lancer EX and Mirage units required camshaft replacement before 120,000 km, while UK DVSA records show minimal emissions failures due to mechanical simplicity. Extended timing belt intervals and use of incorrect oil increase cam wear, making fluid and belt maintenance critical.
Analysis derived from Mitsubishi technical bulletins (1984–1995) and UK DVSA failure statistics (1995–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MITSUBISHI 4G12.
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