The 1987 Plymouth Reliant is a vehicle that defined an era of practical transportation, combining economy with surprisingly capable handling. However, keeping this classic American sedan running smoothly requires more than just basic maintenance; it demands the right lubricants tailored to its specific mechanical needs. The 2.5-liter engine, known for its durability, benefits significantly from the advanced protection offered by modern synthetic oils, which outperform conventional fluids in preventing wear, sludge buildup, and oil consumption. Whether you are driving your Reliant daily, using it for weekend cruises, or letting it sit in storage, choosing the correct viscosity and fluid type is critical to extending the vehicle’s lifespan.
Proper lubrication matters immensely for this vehicle because its aging internal components are prone to sludge accumulation and seal hardening over time. The Reliant’s engine, while robust, operates under conditions that can cause conventional oils to break down, leading to increased friction and reduced fuel efficiency. By utilizing high-performance AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil, AMSOIL Extended-Life 5W-30 100% Synthetic Motor Oil, AMSOIL OE 5W-30 100% Synthetic Motor Oil, and AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil combined with compatible WIX Oil Filter or AMSOIL Oil Filter, owners can mitigate the effects of age and mileage. These advanced fluids provide superior thermal stability, ensuring the engine remains cool under load and maintains proper lubrication during cold starts, which is when most engine wear occurs. Furthermore, the 2.5-liter engine’s 4-quart oil capacity is easily met by premium filters and oils designed to last up to 25,000 miles, reducing the frequency of maintenance intervals and keeping the engine cleaner for longer.
Recommended AMSOIL Products
To ensure your 1987 Plymouth Reliant receives the best possible care, we have selected the top-tier fluids and filters specifically matched to its 2.5L engine specifications. These products are designed to deliver maximum protection against wear, corrosion, and deposits.
- AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil – Offers the highest level of engine protection with a unique blend of synthetic base stocks that provide 75% more protection against horsepower loss and wear. It is ideal for drivers seeking extended performance up to 25,000 miles.
- AMSOIL Extended-Life 5W-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, making it a cost-effective choice for regular maintenance.
- AMSOIL OE 5W-30 100% Synthetic Motor Oil – Fights sludge and deposits with 100% synthetic formulation. It provides robust engine protection for vehicles meeting GM dexos1 Gen 2 specifications.
- AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil – Features unique chemistry for vehicles with over 75,000 miles, offering boosted detergent and dispersant packages to help engines last longer and perform better.
- AMSOIL Oil Filter – Provides 99 percent filtering efficiency at 20 microns, capturing wear-causing contaminants to keep the engine clean and reducing wear. Its higher capacity design ensures better protection for small, abrasive particles.
- WIX Oil Filter – Features premium media offering improvements over original equipment manufacturer (OEM)-branded filters, ensuring reliable filtration for conventional oil protection intervals.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A unique OAT formulation that protects cooling system metals, gaskets, and hoses for up to 150,000 miles or 5 years. It is phosphate- and silicate-free, ensuring compatibility with a wide range of cooling system components.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated option requiring mixing with distilled water, offering similar corrosion protection and extended service life up to 150,000 miles or 5 years.
- AMSOIL Signature Series Multi-Vehicle 100% Synthetic Automatic Transmission Fluid – Designed to withstand heavy towing and elevated temperatures while remaining fluid in sub-zero conditions. It protects against wear and helps maintain smooth, shudder-free shifts.
- AMSOIL OE Multi-Vehicle 100% Synthetic Automatic Transmission Fluid – Protects against wear, resists harmful sludge, and promotes smooth, shudder-free shifts for vehicles requiring OE specifications.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Features a stable viscosity over a wide temperature range, providing excellent ABS and traction-control responsiveness. It resists moisture contamination to ensure reliable stopping power in all weather conditions.
- AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid – Reduces friction, helps seals remain soft to prevent leaks, and resists heat for long fluid life while providing strong anti-wear protection.
Transmission and Manual Gearbox Care
The 1987 Plymouth Reliant came equipped with both automatic and manual transmission options, each requiring specific fluid characteristics to ensure longevity. For the 3-speed automatic transmissions like the A404 and A670, a high-quality synthetic fluid is essential. These transmissions benefit from AMSOIL’s Multi-Vehicle Automatic Transmission Fluid, which resists sludge formation and protects against leaks caused by seal degradation. The automatic transmission capacity is approximately 8.3 quarts for a total fill on the A404, and 8.9 quarts for the A670, with initial fills requiring around 4 quarts. Using a synthetic fluid helps maintain the correct friction characteristics for the clutches and bands, preventing the shudder and slipping issues that often plague older automatics.
Owners with manual transmissions should note that the 4-speed and 5-speed models have specific requirements. These gearboxes typically require 3.8 pints to 4.4 pints of fluid. While the source material highlights motor oil for certain manual transmission applications, utilizing a high-quality Signature Series Motor Oil, AMSOIL OE Motor Oil, or Extended-Life Motor Oil for the fill is often recommended for smoother shifting and gear protection. The fill plug torque for the manual transmission is specified at 24 ft/lbs. Proper lubrication here ensures that the synchronizers and bearings remain free of wear, extending the life of the gearbox significantly.
Cooling System and Brake Fluid Recommendations
The cooling system in the Reliant requires careful attention to prevent overheating, a common issue in older vehicles where radiators or water pumps may show signs of age. The system capacity is approximately 9 quarts. AMSOIL’s Passenger Car & Light Truck Antifreeze & Coolant provides a robust defense against corrosion and cavitation, protecting aluminum and steel components. Its pre-mixed formulation ensures a 50/50 ratio that offers protection down to -34°F and boils at 229°F, providing a critical safety margin. For those who prefer to mix their own, the Propylene Glycol Antifreeze is a concentrated option that offers similar protection and can be mixed with distilled water to achieve the desired freeze point.
Brake fluid is another critical fluid that is often overlooked until performance issues arise. The Reliant uses DOT 3 and DOT 4 fluids. Over time, brake fluid absorbs moisture from the air, which lowers its boiling point and can lead to a spongy pedal or brake fade. AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid resists this moisture absorption far better than conventional fluids, maintaining a high boiling point and ensuring consistent pedal feel. This is particularly beneficial for a vehicle that may have seen decades of use, as fresh synthetic fluid helps restore the hydraulic system’s efficiency.
Power Steering and Fuel System Protection
Power steering systems in the 1987 Reliant benefit greatly from synthetic fluids that reduce friction and keep seals soft. The AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid is formulated to resist heat and prevent leaks, which are common problems as the vehicle ages. It contains anti-wear additives that protect the pump and rack, ensuring quiet and responsive steering. Using a synthetic fluid extends the life of the seals, preventing the hardening that leads to leaks and fluid loss.
For fuel system maintenance, the AMSOIL P.i. Performance Improver Gasoline Additive is a powerful tool for restoring lost horsepower. It cleans injectors and intake valves, improving fuel economy and engine responsiveness. For vehicles that are driven infrequently or stored for long periods, AMSOIL Gasoline Stabilizer helps keep fuel fresh for up to 12 months, preventing varnish and gum buildup that can clog carburetors or fuel injectors. Additionally, AMSOIL Upper Cylinder Lubricant provides extra protection for the upper engine components, further reducing wear and preventing rust during storage or in cold climates. For extended storage, AMSOIL Engine Fogging Oil is a highly-effective rust preventive designed to protect internal engine components during long periods of inactivity.
About the Vehicle
The 1987 Plymouth Reliant occupies a unique place in automotive history as part of the “K-car” family, a platform that revolutionized the American compact car market. Developed by Chrysler in the late 1970s and into the 1980s, the Reliant was one of the first American front-wheel-drive cars to gain widespread acceptance. It was designed with economy and practicality in mind, offering a spacious interior for its compact footprint. The 2.5-liter 4-cylinder engine, identified by engine code [K] in the 1987 model year, was known for its simplicity and reliability, though it was not a high-performance powerhouse. It produced modest horsepower but was praised for its fuel efficiency and ease of maintenance, making it a favorite for families and budget-conscious buyers.
Despite its reputation for durability, the Reliant is not without its known issues, which can be effectively managed or mitigated through proper lubrication. One common problem is engine oil consumption, often caused by hardened valve stem seals or worn piston rings as the vehicle ages. The use of high-mileage synthetic oils with enhanced sealing additives, such as AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil, can help reduce this consumption and prevent oil leaks. Another frequent issue is sludge buildup in the engine, particularly in vehicles that have undergone short-trip driving or infrequent oil changes. Synthetic motor oils, with their superior cleaning capabilities, help dissolve and suspend these deposits, preventing them from clogging oil passages and starving components of lubrication.
Transmission slippage is a third concern for Reliant owners, especially those with the older automatic transmissions. Over time, the friction modifiers in standard fluids break down, leading to harsh or slipping shifts. Switching to a high-quality synthetic transmission fluid, such as Signature Series Automatic Transmission Fluid or AMSOIL OE Multi-Vehicle Automatic Transmission Fluid, can restore proper friction characteristics and extend the service life of the transmission. Additionally, cooling system failures can occur due to rust and corrosion within the radiator and water pump. Using a high-performance antifreeze that contains modern corrosion inhibitors, like AMSOIL Passenger Car & Light Truck Antifreeze & Coolant, can prevent these issues, ensuring the engine stays cool and operates at peak efficiency. Finally, power steering leaks are a common annoyance in older Chrysler vehicles, often due to seal degradation. A synthetic power steering fluid helps keep these seals pliable, preventing leaks and maintaining smooth steering operation for years to come.