Maintaining a 1987 GMC Suburban with the 5.7L 8-cylinder engine requires a commitment to high-quality lubricants that can withstand the demands of a full-size SUV. Whether you are hauling loads, towing, or simply driving daily, the longevity of your vehicle depends on using fluids that offer superior protection against wear, heat, and contamination. AMSOIL synthetic lubricants are engineered to exceed industry standards, providing unmatched engine protection and extended drain intervals compared to conventional oils.
Recommended AMSOIL Products
- AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil – The ultimate protection with up to 25,000 miles of guaranteed protection between oil changes, offering 75% more engine protection against horsepower loss and wear.
- AMSOIL Extended-Life 5W-30 100% Synthetic Motor Oil – Provides 37% more cleaning power than OE oil to keep your engine running smoother for up to 20,000 miles.
- AMSOIL OE 5W-30 100% Synthetic Motor Oil – A cost-effective 100% synthetic option that fights sludge and deposits while delivering performance that outperforms conventional oils.
- AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil – Specially formulated for vehicles with over 75,000 miles, featuring reduced sludge by 67% and boosted detergents to keep aging engines healthy.
- AMSOIL Oil Filter – Offers filtering efficiency of 99 percent at 20 microns, allowing lower restriction and greater capacity for contaminants to help reduce engine wear.
- WIX Oil Filter – A premium media option that offers improvements over original equipment manufacturer-branded filters for reliable filtration.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A unique poly-organic acid (OAT) formulation protecting cooling system metals, gaskets, and hoses for up to 150,000 miles.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated antifreeze solution that provides protection up to 150,000 miles or 5 years, vastly surpassing standards for corrosion and erosion.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Designed to withstand the rigors of heavy towing and elevated temperatures while remaining fluid in sub-zero conditions.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – A reliable OE specification fluid that protects against wear and ensures smooth shifting in automatic transmissions.
- WIX Transmission Filter – Premium media designed to improve upon OEM filters for both 3-speed and 4-speed transmissions in this vehicle.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Provides excellent ABS and traction-control responsiveness with stable viscosity over a wide temperature range.
- AMSOIL SEVERE GEAR® 80W-90 100% Synthetic Gear Lube – Advanced protection against wear that controls thermal runaway and protects against rust in differentials and transfer cases.
- AMSOIL SEVERE GEAR® 75W-90 100% Synthetic Gear Lube – An alternative gear lube offering long oil, seal, and equipment life with friction modifiers for limited-slip applications.
- AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid – Reduces friction and helps seals remain soft to prevent leaks while providing excellent high-temperature protection.
- AMSOIL P.i.® Performance Improver Gasoline Additive – Restores up to 14% horsepower and cleans fuel injectors to 100% flow rate after one tank of fuel.
Understanding the correct fluid capacities and specifications is vital for the health of your 1987 GMC Suburban. For the engine oil, the 5.7L V8 requires 5 quarts when the filter is changed, with a torque specification of 20 ft/lbs for the oil drain plug. It is crucial to check the oil level after refilling to ensure proper lubrication. The cooling system is substantial, requiring 17.4 quarts if the vehicle has air conditioning, or 18 quarts if it does not. AMSOIL’s antifreeze formulations are pre-mixed ethylene glycol solutions that protect all cooling system metals, gaskets, and hoses while being phosphate, nitrate, and silicate-free.
When addressing the drivetrain, the automatic transmission requires specific attention based on the transmission type. The 3-speed THM400 holds 10.6 quarts for a total fill, with an initial fill capacity of 4.3 quarts. The 4-speed THM700-R4, another common option for this era, requires 11.5 quarts for a total fill and 5 quarts for an initial fill. Note that manufacturer specifications have updated from Dexron II or III to Dexron VI, making a high-performance synthetic fluid essential for shifting quality and durability. The manual transmission does not have a specific AMSOIL recommendation in the current guide, so checking the original equipment specification is advised. For the transfer case, capacities vary by the specific model, such as the NP205 which holds 5.1 pints, or the NP208 which requires 10.1 pints. The differential lubrication depends heavily on the gear ratio, with capacities ranging from 3.6 pints for a rear 8.8 RG to 13.9 pints for a rear 12.25 RG. All differential and transfer case applications call for GL-5 rated synthetic gear lubes to handle the extreme pressure of the vehicle’s heavy-duty duties.
Essential Maintenance for the 1987 GMC Suburban
Beyond the engine and transmission, the 1987 GMC Suburban benefits significantly from regular maintenance of its brake and steering systems. The brake system utilizes hydraulic fluid meeting DOT 3 specifications. Upgrading to a synthetic DOT 3 and DOT 4 100% Synthetic Brake Fluid can provide a higher boiling point, which is critical for maintaining consistent pedal feel under heavy loads or repeated stops. For the power steering system, the vehicle is equipped with a pump requiring specific lubrication. AMSOIL’s 100% synthetic multi-vehicle Power Steering Fluid resists heat and oxidation, reducing friction and helping to keep seals soft to prevent common leaks found in older vehicles. This fluid is formulated for quiet operation, ensuring smooth steering response as the vehicle ages.
Fuel system health is another critical area for maintaining the performance of this classic V8 engine. Carbon buildup can reduce efficiency and power over time. The AMSOIL P.i.® Performance Improver gasoline additive is designed to restore fuel injectors to 100% flow rate, effectively cleaning the fuel system and helping to prevent carbon rap. This additive is compatible with capless fuel systems and can help reduce the need for higher-octane fuel by improving combustion efficiency. For vehicles that are stored seasonally, such as those used for winter vacations or summer towing, using a Gasoline Stabilizer keeps fuel fresh for up to 12 months, protecting against varnish and gum buildup caused by ethanol corrosion. Additionally, an Engine Fogging Oil can be used to coat internal components during long periods of inactivity, preventing rust and ensuring the engine starts smoothly when it is time to drive again.
About the Vehicle
The 1987 GMC Suburban stands as a testament to American automotive engineering, representing the culmination of a design philosophy that prioritized durability, utility, and ruggedness. As a full-size SUV, it was built on the GMT400 platform, a nameplate that would go on to define GMC’s heavy-duty trucks and SUVs for decades. The Suburban of this era was not merely a passenger vehicle; it was a workhorse designed to haul cargo, tow trailers, and transport large families through a variety of terrains. The 5.7L 8-cylinder engine, known internally as the L05 or Vortec 250 V8 depending on specific tuning and production changes during that period, provided a balance of torque and reliability that was essential for the Suburban’s duties. This engine family was renowned for its robust construction and ability to run on regular unleaded fuel, making it accessible and practical for daily use.
Owners of the 1987 Suburban typically appreciate the vehicle’s exceptional space and versatility. The interior offered seating for up to nine passengers, with removable rear seats that allowed for flexible cargo configurations. Whether used for family road trips, commercial hauling, or as a personal luxury cruiser, the Suburban’s commanding presence on the road was undeniable. The ride quality, while not as refined as modern unibody SUVs, was characterized by a sense of stability and solidity that many drivers find missing in contemporary vehicles. The suspension system was designed to handle heavy loads without bottoming out, making it a preferred choice for those who needed to tow boats, campers, or heavy equipment.
Despite its reputation for toughness, the 1987 GMC Suburban does face some common issues that owners should be aware of. One of the most prevalent problems is related to the cooling system, where overheating can occur due to aging radiators, thermostats, or water pumps. The aluminum engine heads, while lightweight, can be susceptible to cracking if the engine overheats significantly, which is why maintaining proper coolant levels and using a high-quality antifreeze is crucial. Another common area of concern is the transmission, particularly the 3-speed automatic. With high mileage, these transmissions can develop shifting issues or slippage, often due to worn clutch packs or solenoids. Using a high-performance synthetic transmission fluid can help mitigate wear and improve shifting smoothness, extending the life of the unit.
Electrical issues are also a known challenge for vehicles of this vintage. Corrosion in wiring harnesses and connectors can lead to intermittent problems with lights, gauges, or the ignition system. The fuel system, specifically the carburetor or early fuel injection systems, can suffer from varnish buildup or clogged jets if the vehicle sits for extended periods. Regular maintenance with fuel additives and stabilizers can prevent these issues. Furthermore, the brake system can experience a loss of pressure or a spongy pedal feel due to brake fluid absorbing moisture over time. Flushing the brake fluid and replacing it with a synthetic DOT 3 fluid ensures consistent braking performance and protects the calipers and master cylinder from internal corrosion. By addressing these potential problem areas with the right synthetic lubricants and additives, owners can significantly reduce the likelihood of costly repairs and keep their 1987 GMC Suburban running as smoothly as the day it rolled off the assembly line.