Maintaining the mechanical integrity of your 1987 Mitsubishi Montero requires more than just regular service; it demands the right fluids to protect its aging 2.6-liter engine and drivetrain components. This classic SUV, powered by the robust Mitsubishi 4G62 engine, was designed for rugged terrain, but decades of use can lead to wear, oil leaks, and fluid degradation. Selecting high-quality synthetic lubricants is the most effective way to restore performance, reduce operating temperatures, and extend the vehicle’s operational life. Whether you are tackling steep trails or simply cruising to the store, the correct oil changes can mitigate common issues associated with older Japanese four-cylinder engines.
Recommended AMSOIL Products
- AMSOIL Signature Series 10W-30 100% Synthetic Motor Oil – Provides maximum protection against horsepower loss and wear with a viscosity grade ideal for the 1987 Montero’s 2.6L engine.
- AMSOIL Extended-Life 10W-30 100% Synthetic Motor Oil – Offers superior cleaning power and guaranteed protection for up to 20,000 miles between oil changes.
- AMSOIL OE 10W-30 100% Synthetic Motor Oil – An excellent choice formulated to fight sludge and deposits, ensuring the engine stays clean over time.
- AMSOIL 10W-30 100% Synthetic High-Mileage Motor Oil – Specifically designed for vehicles with over 75,000 miles to reduce oil consumption and sludge buildup.
- WIX Oil Filter – Premium media that offers improvements over original equipment manufacturer filters to ensure clean oil circulation.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A ready-to-use 50/50 pre-mix that protects the cooling system for up to 150,000 miles or 5 years.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated, phosphate-free formula requiring mixing, offering excellent protection against corrosion and erosion.
- AMSOIL 75W-90 Manual Transmission & Transaxle Gear Lube – Perfect for the manual transmission, providing excellent seal compatibility and protection for brass synchronizers.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Ensures excellent ABS and traction-control responsiveness with a stable viscosity over a wide temperature range.
- AMSOIL SEVERE GEAR® 80W-90 100% Synthetic Gear Lube – Advanced protection for front and rear differentials that controls thermal runaway and protects limited-slip applications.
- AMSOIL SEVERE GEAR® 75W-90 100% Synthetic Gear Lube – Delivers extended oil, seal, and equipment life with superior protection against wear and rust.
- AMSOIL SEVERE GEAR® 75W-110 100% Synthetic Gear Lube – A heavy-duty option for extreme conditions, maintaining viscosity under high pressure and temperature.
- AMSOIL Signature Series Multi-Vehicle 100% Synthetic Automatic Transmission Fluid – Withstands heavy towing and elevated temperatures while remaining fluid in sub-zero conditions.
- AMSOIL OE Multi-Vehicle 100% Synthetic Automatic Transmission Fluid – Promotes smooth, shudder-free shifts and guards against leaks for standard automatic transmissions.
The engine in your 1987 Montero is a 2.6-liter four-cylinder, often identified by the engine code [E]. This powerplant, part of Mitsubishi’s legendary 4G6 family, was renowned for its durability and simplicity, making it a favorite for off-road enthusiasts who rely on reliability above all else. However, as these engines age, the oil inside breaks down, leading to increased sludge and wear. The recommended oil capacity for a 1987 Montero with a filter change is 6 quarts. Using AMSOIL’s Signature Series or Extended-Life options ensures that the oil maintains its viscosity and protective properties far longer than conventional oils. This extended protection is crucial for engines that may have seen significant wear, as the synthetic formulation helps reduce oil consumption and maintains proper lubrication during the high-stress cycles typical of off-road driving.
Beyond the engine, the drivetrain of the Montero requires specific attention. The manual transmission, if equipped, specifies a GL-4 lubricant. The standard recommendation calls for 5.3 pints, and using a friction-modified synthetic gear lube like AMSOIL 75W-90 Manual Transmission & Transaxle Gear Lube is essential for smooth shifting and protecting the brass synchronizers that can wear out in older units. For the differential units, the requirements vary by ambient temperature. For front differentials operating in colder climates or standard rear differentials, 2.3 pints of 80W-90 or similar viscosity is typically required. For limited-slip differentials, a special friction modifier is often needed, making the use of a high-performance synthetic gear lube like AMSOIL SEVERE GEAR® 80W-90 or 75W-90 vital for preventing chatter and ensuring power delivery to all wheels. These fluids not only protect the gears from wear but also help maintain the thermal stability required for sustained off-road use.
Fluids like coolant and brake fluid are often overlooked but are critical for safety and engine longevity. The cooling system holds approximately 8.5 quarts. A pre-mixed antifreeze like AMSOIL Passenger Car & Light Truck Antifreeze & Coolant or a concentrated propylene glycol alternative provides superior heat transfer and corrosion protection compared to traditional green coolants. For the braking system, the Montero utilizes hydraulic DOT 3 brake fluid. Switching to AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid ensures consistent pedal feel and prevents the fluid from absorbing moisture, which can lead to boiling and brake failure. Finally, the power steering system, which relies on automatic transmission fluid, benefits from a synthetic fluid that resists oxidation and foaming, helping to preserve the pump and rack for years to come.
About the Vehicle
The 1987 Mitsubishi Montero represents a pivotal era in the history of sport utility vehicles. Originally known as the “Pajero” in international markets, the Montero was Mitsubishi’s answer to the growing demand for capable, mid-size 4×4 vehicles that could handle both daily commuting and serious off-road adventures. Unlike the boxy, body-on-frame trucks of the era, the Montero offered a blend of rugged capability with a more refined driving experience, setting a precedent for the modern SUV market.
The first generation of the Montero was powered by a 2.6-liter four-cylinder engine, known internally as the 4G62. This engine was a naturally aspirated, overhead cam unit that produced modest but adequate power for a vehicle of its size. While it lacked the raw horsepower of larger V6 engines found in competitors, the 4G62 was celebrated for its longevity and mechanical simplicity. It was a “workhorse” engine, designed to be rebuilt and maintained with ease, which resonated deeply with owners who valued reliability over speed. The engine’s compact design allowed for better weight distribution, contributing to the vehicle’s agility on trails.
Owners of this vehicle often appreciate its distinctive blend of utility and character. The Montero was one of the first SUVs to offer a genuine choice between two-wheel drive and four-wheel drive, with a robust transfer case that allowed drivers to switch modes as needed. Its independent front suspension (in later models) and solid rear axle provided a comfortable ride on pavement while maintaining traction in mud, snow, and rocks. The vehicle’s market position was unique; it was a practical family hauler that doubled as a legitimate off-roader, appealing to families who needed a reliable vehicle for weekend getaways and mountain roads.
Despite its rugged reputation, the 1987 Montero does face common problems associated with its age and design. One of the most prevalent issues is oil sludge buildup in the engine, particularly if the vehicle has been operated with non-synthetic oils for long periods. The oil pan on this model can accumulate significant sludge, which restricts oil flow to critical components like the timing chain and oil pump. Using a high-detergent synthetic oil helps break down existing sludge and prevent new deposits from forming, restoring proper oil pressure and engine health.
Another common challenge is the degradation of the cooling system. Over decades, the original cooling system components can become clogged with rust and scale, leading to overheating issues, especially under load. The engine’s cooling capacity is sensitive, and a failing thermostat or worn radiator can cause the engine to run hotter than designed. A high-performance antifreeze that protects against corrosion and offers superior heat transfer can be the difference between a reliable drive and a blown head gasket. Additionally, the transfer case and differential seals can harden and leak over time, leading to fluid loss. Synthetic gear lubes offer better seal conditioning and higher thermal stability, which helps keep these seals pliable and prevents leaks.
Furthermore, the manual transmission in many of these early models can suffer from synchronizer wear, resulting in difficult shifts or grinding noises. This is often due to the breakdown of the original gear oil, which loses its friction-modifying properties. Upgrading to a dedicated manual transmission fluid that includes anti-wear additives and friction modifiers ensures smoother engagement of gears and protects the brass synchros. Finally, the brake fluid in these older hydraulic systems can absorb moisture, leading to a spongy brake pedal and reduced stopping power. Switching to a high-quality synthetic brake fluid helps maintain a firm pedal and prevents internal corrosion in the brake lines and calipers. By addressing these specific areas with the right lubricants, owners can keep their 1987 Montero running smoothly for years to come.