Maintaining your 1985 Toyota Supra with the 2.8L 6-cylinder engine code M 5M-GE requires a strategic approach to lubrication. This classic vehicle features a precision inline-six engine that relies heavily on proper fluid dynamics to maintain its performance, handling, and longevity. Whether you are cruising on modern highways or preparing the car for a historic rally, using the correct viscosity and chemical formulation is essential. The engine oil must protect against wear while managing the heat generated by the high-revving nature of the 5M-GE. Beyond the crankcase, the transmission, differential, and cooling systems have specific fluid requirements that differ from modern cars. Selecting the right synthetic fluids ensures smooth gear shifts, prevents corrosion in the cooling system, and provides reliable stopping power for the brake system.
Recommended AMSOIL Products
- AMSOIL Signature Series 10W-30 100% Synthetic Motor Oil – Offers unmatched protection with up to 25,000 miles of service life and superior engine cleanliness for this classic inline-six.
- AMSOIL Extended-Life 10W-30 100% Synthetic Motor Oil – Provides a robust balance of cleaning power and protection, ideal for vehicles requiring 20,000 miles between changes.
- AMSOIL OE 10W-30 100% Synthetic Motor Oil – A budget-friendly synthetic option that fights sludge and deposits while maintaining OEM performance standards.
- AMSOIL 10W-30 100% Synthetic High-Mileage Motor Oil – Specifically formulated for vehicles with over 75,000 miles, featuring boosted detergents and seal conditioners to reduce sludge.
- AMSOIL Oil Filter EA15K51 – Delivers 99% filtration efficiency at 20 microns with a metal face seal and extended service life to protect your engine from wear.
- WIX Oil Filter 51348 – Features premium media that offers improvements over standard OEM filters, ensuring clean oil circulation.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A pre-mixed 50/50 solution that exceeds OEM requirements for protection up to 150,000 miles or 5 years.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated formula offering exceptional corrosion protection and a service life of up to 150,000 miles.
- AMSOIL Signature Series Multi-Vehicle 100% Synthetic Automatic Transmission Fluid – Withstands extreme temperatures and heavy towing while providing reserve protection during intense driving conditions.
- AMSOIL OE Multi-Vehicle 100% Synthetic Automatic Transmission Fluid – Promotes smooth, shudder-free shifts and guards against leaks for both automatic and power steering applications.
- AMSOIL SEVERE GEAR® 75W-90 100% Synthetic Gear Lube – Ideal for manual transmissions and differentials, featuring friction modifiers for limited-slip applications and thermal runaway protection.
- AMSOIL SEVERE GEAR® 75W-110 100% Synthetic Gear Lube – A thicker viscosity option for heavy-duty use or extreme cold, controlling wear and rust effectively.
- AMSOIL SEVERE GEAR® 80W-90 100% Synthetic Gear Lube – Perfect for rear differentials above -18°C, offering advanced wear protection and reduced operating temperatures.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Provides excellent responsiveness for ABS and traction control systems with a stable viscosity range.
Engine Oil and Filtration for the 5M-GE
The heart of your 1985 Toyota Supra is the 2.8-liter inline-six engine, specifically the 5M-GE model. This engine was engineered for high-revving performance and efficiency, requiring oil that can handle thermal stress without breaking down. The recommended oil grade is 10W-30, with a total capacity of 5.4 quarts including the filter. After refilling, it is critical to check the oil level to ensure it is correct. The oil drain plug requires a torque specification of 25 ft-lbs to prevent leaks or stripped threads.
For owners seeking maximum longevity, the AMSOIL Signature Series 10W-30 is the top-tier choice. This 100% synthetic oil provides up to 25,000 miles of protection, significantly reducing horsepower loss and wear. Its advanced formulation is particularly beneficial for the 5M-GE’s valvetrain and piston rings, ensuring the engine runs smoothly whether you are driving on a track or enjoying a weekend cruise. The oil also boasts 75% more engine protection against horsepower loss and wear compared to conventional oils.
For those who prefer a slightly longer interval or a robust everyday solution, the AMSOIL Extended-Life 10W-30 offers up to 20,000 miles of service life. It contains 37% more cleaning power than the OE version, helping to keep the engine cleaner and reducing the accumulation of deposits that can plague older vehicles. If your driving habits are more conservative or you are budget-conscious, the AMSOIL OE 10W-30 provides reliable protection while fighting sludge. For Supras that have accumulated significant mileage, such as those over 75,000 miles, the AMSOIL 10W-30 High-Mileage is highly recommended. It features unique chemistry with boosted detergents and reduced sludge by 67%, helping to rejuvenate an aging engine.
Proper filtration is just as vital as the oil itself. The AMSOIL Oil Filter is designed to work in harmony with synthetic oils. It filters at 99% efficiency at 20 microns and features a metal face seal to prevent bypassing. This filter allows for lower restriction, ensuring parts are always lubricated, and has greater capacity for contaminants than competing filters. Alternatively, the WIX Oil Filter serves as a high-quality OEM-comparable option, offering premium media that improves upon standard manufacturer filters.
Transmission and Differential Lubrication
The 1985 Supra 2.8L came with both automatic and manual transmission options, each requiring specific lubricants to ensure shifting precision and durability. For the 4-speed automatic transmission (model A40D), the total fill capacity is 6.9 quarts, with an initial fill of 2.5 quarts. Maintaining the automatic transmission fluid is crucial for protecting the transmission from wear, sludge, and temperature-related issues. The AMSOIL Signature Series Multi-Vehicle ATF is designed to withstand the rigors of heavy use, remaining fluid in sub-zero temperatures while providing reserve protection during high-load conditions. For those needing a fluid that promotes smooth, shudder-free shifts, the AMSOIL OE Multi-Vehicle ATF is an excellent choice that also works for power steering systems requiring DEXRON-III specifications.
For the manual transmission (5-speed W58) and the rear differential, synthetic gear lubes are recommended. The manual transmission requires 4.9 pints of lubricant. For the rear differential, the capacity is 2.5 pints for standard GL-5 applications above -18°C, or 80W-90 viscosity for below -18°C. Limited-slip differentials require specific fluids designed to handle the clutch packs found in these units. The AMSOIL SEVERE GEAR® 75W-90 is a versatile option for manual transmissions and limited-slip differentials, containing friction modifiers and protecting against rust and corrosion. If you operate in extremely cold temperatures, the AMSOIL SEVERE GEAR® 75W-110 provides a thicker film strength. For rear differentials in moderate conditions, the AMSOIL SEVERE GEAR® 80W-90 offers a balance of protection and flow, helping to reduce operating temperatures and extend equipment life.
Coolant and Brake Fluid Systems
The cooling system in the 1985 Toyota Supra holds 8.5 quarts of fluid. Using the correct antifreeze and coolant is essential to prevent corrosion, which can be a significant issue in older vehicles. The AMSOIL Passenger Car & Light Truck Antifreeze & Coolant is a pre-mixed 50/50 solution that is compatible with all other antifreeze colors and protects against corrosion for 150,000 miles. It is phosphate, nitrate, and silicate-free, making it safe for all cooling system metals and gaskets. For those who prefer a concentrated product or require high-performance cooling, the AMSOIL Propylene Glycol Antifreeze and Engine Coolant is a premium choice. This concentrated formula allows for precise mixing and offers superior protection against metallic corrosion and erosion, extending service intervals significantly.
The braking system on the Supra requires a fluid that maintains stability under heavy use. The vehicle specifies a DOT 3 hydraulic brake fluid. The AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid is an excellent upgrade for this system. It provides excellent responsiveness for ABS and traction control, ensuring that braking performance remains consistent even after multiple hard stops. Its stable viscosity over a wide temperature range ensures that the brake pedal feel remains firm, providing confidence when driving this high-performance sports car.
Additional Maintenance and Protection
Beyond the essential lubricants and fluids, there are other products that can enhance the performance and preservation of your 1985 Toyota Supra. For seasonal storage, preventing fuel degradation is critical. The AMSOIL Gasoline Stabilizer helps keep fuel fresh for up to 12 months, protecting against varnish, gum buildup, and ethanol corrosion. This is particularly useful for vehicles that are driven infrequently or stored for winter. Similarly, the AMSOIL Engine Fogging Oil is a highly effective rust preventive designed to protect internal engine components during long periods of inactivity, making it ideal for engines that sit idle for extended times.
To improve fuel system health and engine performance, the AMSOIL P.i.® Performance Improver is a powerful additive. It can restore up to 14% horsepower and cleans fuel injectors to 100% flow rate, which is beneficial for maintaining the efficiency of the 5M-GE’s fuel system. Additionally, for protecting the chassis and bodywork from rust and corrosion, the AMSOIL Heavy-Duty Metal Protector creates a long-lasting, wax-like coating that shields steel, iron, and aluminum from salt and moisture. For cleaning, the AMSOIL Brake and Parts Cleaner quickly removes grease and grime without leaving residue, making it perfect for maintenance on brake components and other mechanical parts.
About the Vehicle
The 1985 Toyota Supra 2.8L is a significant chapter in automotive history, representing the evolution of the Toyota Celica Supra line into a dedicated grand touring sports car. This specific model, powered by the 5M-GE engine, was known for its smooth inline-six configuration, a hallmark of Toyota engineering that offered a balance of power and refinement. The “GE” designation stands for “Gasoline Electronic,” indicating the use of Toyota’s Electronic Fuel Injection (EFI) system, which was a cutting-edge feature at the time, providing better fuel efficiency and throttle response compared to older carbureted systems.
Designed for both spirited driving and long-distance comfort, the 1985 Supra featured a robust chassis that provided excellent handling dynamics. The 2.8-liter engine produced respectable horsepower, making it a competitive choice in the sports coupe market of the mid-1980s. It was built on a platform that prioritized rigidity and weight distribution, contributing to its reputation as a capable track and road car. Owners of this vehicle often appreciate its timeless design, which has aged remarkably well, and the driving experience it offers—a linear and predictable power delivery that allows for precise control.
This generation of the Supra laid the groundwork for the legendary turbocharged models that followed. It was a period when Toyota was establishing itself as a manufacturer of high-quality, reliable sports cars that could stand alongside European competitors. The 5M-GE engine is particularly revered for its durability and potential for tuning, making the 1985 Supra a popular candidate for enthusiasts looking to preserve a classic or restore it to its original glory. Whether used for daily driving or as a show car, maintaining the integrity of its original systems with high-quality lubricants ensures that this classic sports car continues to perform as it was intended.