The 1987 Isuzu Pickup with the 1.9L four-cylinder engine is a rugged workhorse that has seen decades of service on roads and trails. Proper maintenance of this classic vehicle is essential to preserve its reliability, and selecting the correct lubricants is the first step in a long life of service. Whether you are restoring a vintage model or keeping an aging pickup on the road, high-performance synthetic lubricants provide superior protection against wear, corrosion, and thermal breakdown. This guide details the exact fluids, capacities, and recommended products needed to maintain your engine, transmission, and differential systems.
Recommended AMSOIL Products
- AMSOIL Signature Series 10W-30 100% Synthetic Motor Oil – The top-tier choice for maximum engine protection against horsepower loss and wear, offering up to 25,000 miles of guaranteed protection.
- AMSOIL Extended-Life 10W-30 100% Synthetic Motor Oil – Delivers 37% more cleaning power to keep the engine running smoother and lasts up to 20,000 miles between changes.
- AMSOIL OE 10W-30 100% Synthetic Motor Oil – An excellent option for fighting sludge and deposits while providing high-mileage protection at a competitive price point.
- AMSOIL 10W-30 100% Synthetic High-Mileage Motor Oil – Specifically formulated for vehicles with over 75,000 miles to reduce sludge and enhance anti-wear additives.
- WIX Oil Filter – A premium filter option that offers improved media performance over many original equipment manufacturer branded filters.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A 50/50 pre-mix ethylene glycol coolant designed to protect all cooling system metals, gaskets, and hoses for up to 150,000 miles.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated, non-toxic alternative that requires mixing with water, offering protection up to 150,000 miles or 5 years.
- AMSOIL Signature Series Multi-Vehicle 100% Synthetic Automatic Transmission Fluid – Withstands heavy towing, elevated temperatures, and remains fluid in sub-zero conditions for smooth shifting.
- AMSOIL OE Multi-Vehicle 100% Synthetic Automatic Transmission Fluid – Guards against leaks and sludge while promoting shudder-free shifts in automatic transmissions.
- AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil – An optimal choice for extreme cold weather, providing 75% more engine protection than required by industry standards.
- AMSOIL Extended-Life 5W-30 100% Synthetic Motor Oil – Provides 20,000 miles of protection and helps prevent low-speed pre-ignition (LSPI) in modern engines.
- AMSOIL OE 5W-30 100% Synthetic Motor Oil – A cost-effective 100% synthetic option that fights sludge and deposits effectively in 5W-30 applications.
- 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 – Controls thermal runaway and rust in front and rear differentials, ideal for limited-slip applications.
- AMSOIL SEVERE GEAR® 75W-90 100% Synthetic Gear Lube – A premium synthetic gear lube that helps reduce operating temperatures and extends equipment life.
- AMSOIL SEVERE GEAR® 75W-110 100% Synthetic Gear Lube – Offers robust protection against wear for heavier duty applications where a slightly heavier viscosity is preferred.
Engine Oil Selection and Capacities
The 1.9L four-cylinder engine in your 1987 Isuzu Pickup requires a specific viscosity to ensure proper lubrication during operation. The manufacturer specifies SAE 10W-30 as the preferred oil for operating temperatures above -18°C. This grade offers a balance of flow at startup and film strength at operating temperature. For colder climates, 5W-30 is recommended for temperatures below -15°C, while 5W-20 can be used for very cold conditions below -7°C. In hot weather, 10W oil is acceptable, and straight 30-weight oil is suitable for temperatures above 5°C. If you are operating the vehicle in extreme heat, 20W-40 is an option for temperatures above -7°C.
The total oil capacity for the engine, including the filter replacement, is 4.6 quarts. It is critical to pour the correct amount and then check the oil level via the dipstick after the refill to ensure the engine is neither under-lubricated nor overfilled, which could lead to foaming and seal damage. Once the oil is selected, a high-quality filter is mandatory to remove contaminants. The WIX Oil Filter (Code 51381) is a recommended choice that outperforms many OEM-branded filters with its premium media.
For the 1987 Isuzu Pickup, we recommend three primary synthetic engine oils depending on your specific needs. The AMSOIL Signature Series 10W-30 provides the ultimate in protection, extending drain intervals up to 25,000 miles or one year. If you prefer a focus on cleaning and slightly longer intervals for normal service, the AMSOIL Extended-Life 10W-30 offers 37% more cleaning power and a guaranteed 20,000 miles. For those seeking a cost-effective solution without sacrificing synthetic benefits, the AMSOIL OE 10W-30 is an excellent choice that fights sludge and deposits effectively. If your Isuzu has accumulated significant mileage, the AMSOIL 10W-30 High-Mileage version contains boosted detergents and seal conditioners to help older engines run better.
Transmission and Transfer Case Fluids
Keeping the transmission and transfer case properly lubricated is vital for smooth shifting and longevity. For automatic transmissions, specifically the 03-56 and 03-55 models, a total fill capacity of 6.3 quarts is required, with an initial fill of 2.1 quarts during overhaul. Manual transmissions (MSG5R for 4WD and MSG5T for 4WD) require 9.7 pints, while the transfer case requires 3.4 pints. For the transfer case and front differential (GL-5, 90 weight), a capacity of 1.7 pints is needed, and the rear differential (GL-5, 90 weight) requires 3 pints.
AMSOIL offers specialized transmission fluids that outperform conventional oils. The AMSOIL Signature Series Multi-Vehicle Automatic Transmission Fluid is designed to withstand the rigors of heavy towing and high temperatures while maintaining fluidity in sub-zero conditions. Alternatively, the AMSOIL OE Multi-Vehicle Automatic Transmission Fluid offers a reliable, shudder-free shifting experience with excellent protection against wear and sludge. For gear lube, the AMSOIL SEVERE GEAR 80W-90 is an ideal choice for the rear differential, offering protection against rust and corrosion. For those needing extreme performance in the transfer case, AMSOIL SEVERE GEAR 75W-90 or AMSOIL SEVERE GEAR 75W-110 provide superior thermal control and wear protection.
Cooling, Braking, and Other Fluids
The cooling system in your Isuzu holds 9 quarts of coolant. Maintaining the correct mixture is essential to prevent freezing in winter and overheating in summer. The AMSOIL Passenger Car & Light Truck Antifreeze & Coolant is a 50/50 pre-mix formulation that protects all cooling system metals, gaskets, and hoses for up to 150,000 miles. If you prefer a concentrated product, the AMSOIL Propylene Glycol Antifreeze is a non-toxic option that requires mixing with water.
Brake fluid maintenance is often overlooked but critical for safety. The 1987 Isuzu Pickup requires DOT 3 hydraulic brake fluid. The AMSOIL DOT 3 and DOT 4 Synthetic Brake Fluid provides a stable viscosity range, ensuring consistent pedal feel and excellent responsiveness for ABS and traction control systems. It also helps prevent boiling under heavy braking conditions.
For fuel system maintenance, adding a performance improver can restore lost power and improve economy. The AMSOIL P.i.® Performance Improver restores up to 14% horsepower and cleans fuel injectors, which is particularly beneficial for older vehicles where deposits may have accumulated. For seasonal storage, AMSOIL Gasoline Stabilizer keeps fuel fresh for up to 12 months, preventing varnish and gum buildup.
About the Vehicle
The 1987 Isuzu Pickup is part of a lineage of trucks that established Isuzu’s reputation for durability and utility. This era of the vehicle, often referred to by enthusiasts as the “S-Series” or the early generations that would eventually lead to the famous NPR line, was designed for hard work rather than luxury. It features a robust body-on-frame construction that is characteristic of trucks intended for hauling and towing. The 1.9L four-cylinder engine, known for its compact design and reliability, powers this version of the pickup. While it may not compete with the raw torque of a larger V6 or V8 in terms of sheer pulling power, the 1.9L is celebrated for its fuel efficiency and longevity, making it a favorite for those who need a dependable runner for light to moderate loads.
Owners of the 1987 Isuzu Pickup often appreciate its simple, straightforward engineering. The vehicle lacks the complex electronic systems found in modern trucks, which can make it easier for DIY enthusiasts to maintain and repair. The interior is functional and utilitarian, reflecting the no-nonsense approach Isuzu took to its commercial vehicles during the 1980s. The truck was built to handle the demands of rural work, construction sites, and family hauling duties. Its suspension and chassis are tuned to provide a balance between load-carrying capacity and ride quality, although the ride can be firm given its commercial roots.
Despite its age, the 1987 Isuzu Pickup faces specific challenges that owners should be aware of. One common issue with these older engines is oil consumption or leaks around the valve cover gaskets, which can be mitigated by using high-mileage synthetic oils like AMSOIL HM1030 that contain seal conditioners. Another problem is the degradation of cooling system components over time; the rubber hoses and gaskets can dry out and crack, leading to coolant leaks. Using a high-quality antifreeze like AMSOIL Propylene Glycol or the Passenger Car formula helps protect these aging components from corrosion and extends their service life. Additionally, rust is a significant concern for vehicles from this era, particularly in areas that use road salt. Applying protective products like AMSOIL Heavy-Duty Metal Protector can help shield the undercarriage and frame from further corrosion. Finally, transmission issues in these older automatics often stem from worn seals and degraded fluid; using a premium synthetic ATF like AMSOIL Signature Series can help rejuvenate the seals and ensure smooth, reliable shifting for years to come.