The 1987 Buick Skylark equipped with the 2.5-liter four-cylinder engine (Engine Code U) requires specific lubricants to maintain reliability and performance throughout its lifespan. While factory recommendations from the 1980s often suggested conventional oils and standard intervals, modern synthetic fluids offer superior protection against wear, sludge, and extreme temperatures. Using the correct grade and type of fluid is essential for this classic vehicle to ensure smooth operation and longevity.
Recommended AMSOIL Products
For the engine, a 5W-30 viscosity is the primary recommendation for all temperature conditions. The following AMSOIL motor oils provide the best protection for your 1987 Buick Skylark:
- AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil – Offers the highest level of protection with a 25,000-mile service interval, significantly reducing wear and horsepower loss compared to conventional oils.
- AMSOIL Extended-Life 5W-30 100% Synthetic Motor Oil – Delivers 20,000 miles of protection with enhanced cleaning power to keep the engine running smoother for longer.
- AMSOIL OE 5W-30 100% Synthetic Motor Oil – An affordable option that fights sludge and deposits while outperforming conventional oils in OEM-recommended mileage.
- AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil – Formulated specifically for engines with over 75,000 miles to reduce sludge and oil consumption.
Filter selection is equally important to ensure clean oil circulates through the engine. You can choose the AMSOIL Oil Filter for extended service life and superior filtration efficiency, or the WIX Oil Filter for premium media that exceeds OEM standards.
For the cooling system, the 1987 Skylark holds approximately 7.9 quarts of AMSOIL Passenger Car & Light Truck Antifreeze & Coolant. Maintaining a healthy cooling system is critical to prevent overheating and corrosion, especially as the vehicle ages. The AMSOIL Passenger Car & Light Truck Antifreeze & Coolant provides protection up to 150,000 miles or 5 years using a unique OAT formulation. Alternatively, the AMSOIL Propylene Glycol Antifreeze and Engine Coolant is a concentrated option offering superior corrosion protection and extended service intervals.
Transmission maintenance varies depending on whether your Skylark has an automatic or manual transmission. For the automatic transmission (such as the THM125C), the total fill capacity is 6 quarts, with 4 quarts required for an initial fill after a drain. The AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid withstands heavy towing and elevated temperatures, remaining fluid in sub-zero conditions. The AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is an excellent alternative for standard protection against wear. If your vehicle features a manual transmission (such as the MT2 5-speed), the capacity is 5.5 pints. The AMSOIL 5W-30 Manual Synchromesh Transmission Fluid is formulated to improve cold-weather shifting and reduce friction in synchromesh transmissions.
Fluids for other systems should not be overlooked. The braking system requires high-quality fluid to ensure ABS and traction control responsiveness. The AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid provides stable viscosity over a wide temperature range. For power steering, the AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid helps keep seals soft to prevent leaks and resists heat for long fluid life.
About the 1987 Buick Skylark
The 1987 Buick Skylark represents the final chapter of a model line that was deeply embedded in the American automotive landscape for decades. By 1987, the Skylark had evolved significantly from its origins as a personal luxury coupe in the 1960s and a distinct model in the 1970s. For this model year, the Skylark was a compact car built on the General Motors X-body platform, sharing its underpinnings with the Chevrolet Citation and Oldsmobile Firenza. It was designed to be a practical, fuel-efficient family sedan or two-door coupe, positioning itself as a value-oriented alternative in a market increasingly dominated by Japanese imports.
The 2.5-liter inline-four engine, often referred to as the Iron Duke by enthusiasts, was a staple of GM’s small car lineup. While not known for blistering performance, this engine was revered for its durability and simplicity. The “Iron Duke” nickname stems from its cast-iron block and head, which were renowned for their robustness and ability to withstand AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil with proper maintenance. In 1987, this engine typically produced between 90 and 110 horsepower depending on the specific tuning and fuel system (carbureted or fuel-injected), offering sufficient power for daily commuting and highway cruising. The engine code [U] denotes a specific configuration for the 2.5L four-cylinder, often associated with fuel-injected models or specific emission standards for that model year.
Owners of the 1987 Skylark often appreciate the vehicle for its straightforward design and ease of repair. The X-body platform was a common denominator for many GM vehicles, meaning parts were widely available and mechanics were generally familiar with the layout. However, as these vehicles approach 40 years of age, common issues have emerged that regular maintenance can help mitigate. One frequent problem is AMSOIL Propylene Glycol Antifreeze and Engine Coolant system degradation. The aging rubber hoses and the original cooling system components can develop leaks or fail to manage heat efficiently. Using a modern synthetic coolant like AMSOIL’s formulations helps protect against corrosion in the aging metal and keeps the rubber hoses pliable, preventing sudden failures.
Another area prone to wear is the transmission, particularly in vehicles that have seen high mileage. The THM125C automatic transmission found in many Skylarks can develop shifting issues or fluid breakdown over time. High-performance synthetic transmission fluids offer superior friction modifiers and oxidation resistance, helping to smooth out shifts and extend the life of the clutch packs and bands. Additionally, older engines like the 2.5L Iron Duke can suffer from oil sludge accumulation if conventional oils were used historically. The detergents found in modern AMSOIL synthetic motor oils are specifically designed to clean out this sludge and prevent future buildup, ensuring the oil passages remain clear for proper lubrication.
Finally, the brake systems on these older vehicles can sometimes suffer from fluid contamination and a drop in boiling points, leading to brake fade during heavy use. Synthetic brake fluids maintain a higher boiling point and resist moisture absorption better than traditional DOT 3 fluids, ensuring consistent pedal feel and safety. While the 1987 Skylark may not be the sportiest car in the garage, with the right synthetic lubricants, it can remain a reliable, comfortable, and safe daily driver for years to come.