Maintaining the 1987 Buick Somerset with its 2.5L inline-four engine requires specific lubricants to ensure longevity and reliable performance. Proper fluid selection is critical because this vehicle, often used for daily commuting or short trips, operates under conditions that can accelerate oil degradation, fuel dilution, and component wear. Using the correct viscosities and synthetic formulations helps protect against sludge, corrosion, and the specific wear patterns common in older GM powertrains. Whether you are extending service intervals or adhering to traditional maintenance schedules, the right lubricants will maximize the engine’s efficiency and lifespan.
Recommended AMSOIL Products
- AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil – This premium oil offers up to 25,000 miles of protection, superior wear resistance, and excellent high-temperature stability, making it ideal for the 2.5L engine’s needs.
- AMSOIL Extended-Life 5W-30 100% Synthetic Motor Oil – Designed for up to 20,000 miles of protection, this oil provides 37% more cleaning power to keep the engine running smoother and is formulated to resist LSPI and high-temperature coking.
- AMSOIL OE 5W-30 100% Synthetic Motor Oil – A cost-effective option that outperforms conventional oils and is specifically tested to meet GM dexos1 Gen 2 specifications, offering robust protection against wear and sludge.
- AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil – Perfect for Somerset engines with over 75,000 miles, featuring enhanced detergents and seal conditioners to reduce oil consumption and sludge while boosting performance.
- AMSOIL Oil Filter – Delivers 99% filtration efficiency at 20 microns, featuring a stronger media and increased capacity to trap wear-causing contaminants for extended service life.
- WIX Oil Filter – A premium alternative with high-quality media that meets or exceeds original equipment manufacturer specifications, ensuring reliable filtration for the 2.5L engine.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A pre-mixed ethylene glycol formulation that protects cooling system metals, gaskets, and hoses for up to 150,000 miles or 5 years.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated option offering superior corrosion protection and longer service intervals for heavy-duty or demanding driving conditions.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Withstands severe driving, elevated temperatures, and heavy towing while maintaining fluidity in sub-zero conditions for smooth shifting.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Provides excellent wear protection and is formulated to meet the specific requirements of GM automatic transmissions, including THM125C applications.
- AMSOIL 5W-30 Manual Synchromesh Transmission Fluid – Ideal for 5-speed manual transmissions, this fluid reduces friction and heat while improving cold-weather shifting and maximizing fuel economy.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Ensures excellent ABS and traction-control responsiveness with stable viscosity across a wide temperature range for superior stopping power.
- AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid – Reduces friction and keeps seals soft to prevent leaks, offering excellent high and low-temperature performance for quiet operation.
The heart of your 1987 Buick Somerset is the 2.5L inline-four engine, a unit known for its reliability and fuel efficiency during its era. To keep this engine running smoothly, it is vital to adhere to the correct fluid specifications. For the engine oil, a capacity of 3.5 quarts is required when changing the filter. The recommended viscosity is 5W-30 for all temperature conditions, ensuring proper lubrication during cold starts and at operating temperatures. If 5W-30 is not available, 10W-30 can be used, though it is strictly limited to warmer conditions above -18°C or 4°C respectively. When performing an oil change, ensure the oil drain plug is torqued to 25 ft/lbs, and the new filter is installed finger-tight plus an additional 1/4 turn. The cooling system holds 7.9 quarts of coolant, requiring a robust antifreeze to prevent corrosion and freezing in colder climates. For the automatic transmission, specifically the THM125C model, the total fill capacity is 6 quarts, with an initial fill of 4 quarts during overhauls. If your Somerset features the 5-speed manual transmission, the capacity is 5.5 pints, and the fluid requires a specific grade for optimal synchromesh operation.
Proper lubrication is not just about filling a reservoir; it is about the chemistry of the fluid interacting with the metal surfaces inside your vehicle. Modern synthetic oils like the AMSOIL Signature Series offer 75% more protection against horsepower loss and wear compared to conventional oils, which is particularly beneficial for an older engine that may have developed minor clearances. The OE formulation fights sludge and deposits, ensuring that the oil passages remain clear. For the cooling system, using a coolant like AMSOIL’s passenger car and light truck antifreeze provides protection for up to 150,000 miles, preventing the rust and scale buildup that can choke an aging radiator. The transmission fluid is equally critical; the Signature Series ATF is engineered to withstand the rigors of heavy towing and elevated temperatures, preventing the shudder and slip that can occur in older transmissions. Brake fluid, often overlooked, absorbs moisture over time, lowering its boiling point and compromising braking safety. Switching to a synthetic DOT 3 and DOT 4 fluid ensures consistent pedal feel and responsiveness. Finally, the power steering system benefits from a synthetic fluid that keeps seals pliable, preventing the leaks that are common in vehicles of this vintage. By using these specialized products, you are not only following maintenance schedules but are actively extending the life of your Buick Somerset.
About the Vehicle
The 1987 Buick Somerset stands as a notable chapter in American automotive history, representing the final evolution of the compact car platform that began in the early 1980s. Produced by General Motors, the Somerset was designed to compete in the highly competitive compact car segment, offering buyers a badge-engineered sibling to the Chevrolet Citation and Oldsmobile Firenza. The vehicle’s primary selling point was its blend of affordability and practicality, making it a popular choice for budget-conscious families and commuters. Under the hood, the 2.5L inline-four engine code [U] was the most common powerplant, providing a balance of fuel economy and sufficient power for daily driving tasks. While not a high-performance machine, the Somerset was praised for its straightforward engineering and ease of maintenance, which contributed to its durability over the decades.
Owners of the 1987 Buick Somerset often appreciate the vehicle for its simple mechanical layout, which makes it an excellent candidate for DIY enthusiasts. The compact nature of the car means it is agile in traffic and easy to park, a trait that remains valuable even today. However, like many vehicles of its era, the Somerset has some specific areas that require attention as they age. One common issue for these models is the degradation of rubber seals and hoses within the cooling system. Over time, the original rubber components can become brittle, leading to coolant leaks that can quickly overheat the engine if left unaddressed. Using a high-quality synthetic coolant with superior corrosion inhibitors helps preserve the integrity of these older rubber components and metal surfaces. Another frequent problem is oil sludge buildup, particularly in engines that have been operated with conventional oils or have undergone stop-and-go driving. Sludge can restrict oil flow to critical engine parts, leading to accelerated wear and potential engine failure. AMSOIL’s high-performance synthetic oils are specifically formulated to clean out existing sludge and prevent new deposits, ensuring the engine remains clean and efficient.
Transmission wear is another area of concern for 1987 Buick Somerset owners. The automatic transmission, specifically the THM125C, can develop shudder or slipping issues if the fluid has not been changed regularly or if it has degraded over time. Old transmission fluid loses its friction modifiers and can lead to rough shifting or premature wear of internal bands and clutches. Regular fluid exchanges with a high-quality synthetic transmission fluid can alleviate these symptoms and extend the transmission’s service life. Additionally, the brake system on these older cars may suffer from moisture absorption in the brake fluid, which can lower the boiling point and cause spongy pedals or even brake fade in emergency situations. Synthetic brake fluid with a higher boiling point can restore confidence in the vehicle’s stopping power. Finally, the power steering system, relying on aging seals, may develop leaks or become noisy due to stiffening rubber components. A synthetic power steering fluid helps condition these seals, keeping them flexible and preventing the leaks that are so common in vehicles of this vintage. Addressing these specific problems with the correct lubricants ensures that the 1987 Buick Somerset continues to perform reliably for years to come.
Whether you are restoring a classic model or simply maintaining a daily driver, understanding the specific needs of your Buick Somerset is key. The 2.5L engine, while reliable, benefits greatly from the superior stability of synthetic lubricants. By choosing the right AMSOIL products, you are investing in the longevity of your vehicle. From the engine oil that protects against wear to the transmission fluid that ensures smooth shifting, every component works together to keep your Somerset running at its best. With proper care and the right fluids, the Buick Somerset remains a testament to GM’s commitment to producing durable, efficient vehicles.