The Mitsubishi 4G52 is a 1,995 cc, inline‑four naturally aspirated petrol engine produced between 1972 and 1989. It features a single overhead camshaft (SOHC), 8 valves, and a cast‑iron block with an aluminum cylinder head. In standard form it delivered 74–81 kW (100–110 PS) and torque figures between 152–162 Nm, offering robust performance for its era.
Fitted to models such as the Mitsubishi Galant, Lancer, and early Pajero (Shogun), the 4G52 was engineered for durability, simplicity, and ease of service in both passenger and light‑commercial applications. Emissions compliance was achieved through carburettor calibration or early electronic fuel injection, allowing baseline compliance with Japanese Ministry of Transport (JIS D 1001) and pre‑Euro standards.
One documented concern is cylinder head cracking around the exhaust valve seats in high‑load or overheated conditions, highlighted in Mitsubishi Technical Bulletin TB‑78‑03‑045. This issue stems from thermal stress in the original head casting design and marginal coolant flow in the combustion chamber periphery. From 1983, revised head castings with improved coolant jacket geometry were introduced across all applications.
Production years 1972–1982 meet JIS D 1001 standards; 1983–1989 models meet pre‑Euro national standards depending on market (JAMA Type Approval #JAMA/EMS/4G52).
The Mitsubishi 4G52 is a 1,995 cc inline‑four naturally aspirated petrol engine engineered for compact sedans and early SUVs (1972–1989). It combines SOHC valvetrain with a durable cast‑iron block to deliver reliable everyday performance. Designed to meet Japanese JIS and pre‑Euro emissions standards, it prioritizes mechanical simplicity and serviceability over refinement.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,995 cc | |
| Fuel type | Petrol (Unleaded or leaded, depending on year) | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 84.0 mm × 90.0 mm | |
| Power output | 74–81 kW (100–110 PS) @ 5,500–6,000 rpm | |
| Torque | 152–162 Nm @ 3,500–4,000 rpm | |
| Fuel system | Carburettor (early) or throttle-body injection (late) | |
| Emissions standard | JIS D 1001 (1972–1982); pre‑Euro national standards (1983–1989) | |
| Compression ratio | 8.8:1 (carb), 9.2:1 (EFI) | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain‑driven SOHC | |
| Oil type | API SF/SG, SAE 10W‑40 | |
| Dry weight | 138 kg |
The SOHC design provides mechanical simplicity and ease of repair but requires adherence to 7,500 km oil change intervals to prevent sludge buildup and cam wear. API SF/SG (10W-40) oil is critical due to its detergent package protecting the chain-driven valvetrain. Extended intervals or low-detergent oils accelerate sludge formation, particularly in carburetted variants with crankcase dilution. Post-1983 engines feature improved cylinder head castings; pre-1983 units should be inspected for exhaust seat cracking per Mitsubishi TB‑78‑03‑045. The timing chain is designed for life-of-engine service but sensitive to oil contamination—regular oil changes are essential.
Oil Specs: Requires API SF/SG (10W-40) specification (Mitsubishi TB‑78‑03‑045). ACEA A2/B2 oils are acceptable alternatives for EFI variants.
Emissions: JIS D 1001 certification applies to 1972–1982 models only (JAMA Type Approval #JAMA/EMS/4G52). Later builds comply with national pre-Euro standards.
Power Ratings: Measured under ISO 1585 standards. EFI variants require unleaded fuel (RON 91+) for knock prevention (Mitsubishi TIS Doc. FUEL‑4G52).
Mitsubishi Technical Information System (TIS): Docs PETROL‑4G52, TIMING‑4G52, FUEL‑4G52
JAMA Type Approval Database (JAMA/EMS/4G52)
ISO 1585: Road vehicles — Engine test code — Net power
The Mitsubishi 4G52 was used across Mitsubishi's compact and mid‑size platforms with longitudinal or transverse mounting depending on application. This engine received platform-specific adaptations—reinforced mounts in the Pajero and revised oil pan baffling in the Galant—and from 1983 the facelifted Lancer EX adopted updated cylinder heads, 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 distributor mount (Mitsubishi TIS PETROL‑4G52). The 4th and 5th VIN digits indicate engine family ('4G' for 4G52 series). Early engines (1972–1982) have cast-iron valve covers with external rocker arms; post-1983 units use similar covers but with updated head casting numbers. Critical differentiation from 4G54: 4G52 has 1,995 cc displacement vs. 2,555 cc for 4G54. Service parts require production date verification—cylinder head kits for engines before 01/1983 are incompatible with later units due to coolant jacket redesign (Mitsubishi TB‑78‑03‑045).
The 4G52's primary reliability risk is cylinder head cracking around exhaust valve seats in early builds (1972–1982), with elevated incidence in high-load or overheated use. Mitsubishi internal quality data from 1984 indicated up to 11% of pre-1983 engines exhibited head cracks before 180,000 km, while JAMA durability testing confirmed revised heads reduced this to <2% in post-1983 units. Extended oil change intervals and cooling system neglect accelerate thermal stress, making maintenance adherence critical.
Analysis derived from Mitsubishi technical bulletins (1978–1988) and JAMA durability failure statistics (1980–1995). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MITSUBISHI 4G52.
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