Keeping your 1987 BMW 735i running reliably requires more than just starting the engine; it demands a commitment to high-performance lubrication. This classic German sedan features the legendary M30 B35 6-cylinder engine, a powerplant known for its smooth power delivery and robust construction. However, as with any vehicle of this vintage, the wear on internal components, seals, and gaskets increases over time. Proper fluid selection is the difference between a car that rattles and leaks and one that runs quietly and efficiently for years to come. By using the correct viscosity and formulation, you protect the engine against the specific wear patterns associated with flat-tappet camshafts and high-mileage tolerances.
Recommended AMSOIL Products
- AMSOIL Premium Protection 10W-40 100% Synthetic Motor Oil – Ideal for this vehicle with a high-zinc formula designed to guard against wear on flat-tappet cams and resist deposits.
- AMSOIL Extended-Life 10W-40 100% Synthetic Motor Oil – Offers extended protection with superior cleaning power to keep the engine running smoother over long intervals.
- AMSOIL 5W-40 MS 100% Synthetic European Motor Oil – Specifically engineered for the unique demands of gasoline and European vehicles, featuring a precise blend of synthetic base oils.
- MANN-FILTERS Oil Filter – Provides premium filtration with media that offers improvements over original equipment manufacturer branded filters to keep the engine clean.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A unique poly-organic acid formulation that provides protection up to 150,000 miles or 5 years for the cooling system.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated coolant option requiring mixing, offering protection up to 150,000 miles or 5 years in passenger cars.
- AMSOIL Signature Series Multi-Vehicle 100% Synthetic Automatic Transmission Fluid – Withstands heavy towing and elevated temperatures, remaining fluid in sub-zero conditions.
- AMSOIL OE Multi-Vehicle 100% Synthetic Automatic Transmission Fluid – Promotes smooth, shudder-free shifts while guarding against leaks and sludge.
- 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 with friction modifiers for limited-slip applications.
- AMSOIL SEVERE GEAR® 75W-90 100% Synthetic Gear Lube – Controls thermal runaway and reduces operating temperatures for extended gear life.
- AMSOIL SEVERE GEAR® 75W-110 100% Synthetic Gear Lube – Delivers superior protection against wear and rust for heavy-duty gear applications.
The heart of your 1987 BMW 735i is the M30 B35 engine, a 3.5-liter inline-six that has earned a legendary reputation for durability and smooth operation. When servicing this engine, capacity is a critical factor to note. The oil pan holds 6.1 quarts when changing the filter. It is crucial to refill the system with the correct amount and then check the oil level after the refill. If you are looking at the drain plug specifications, you will find a torque setting of 19 mm PBH requiring 43-46 ft/lbs, or a 17 mm PBH requiring 22-26 ft/lbs. Using the correct synthetic viscosity is not just about meeting a specification; it is about ensuring that the oil maintains a protective film between moving parts, especially during the initial startup when the engine is at its most vulnerable. The AMSOIL Premium Protection formula, for instance, includes a high-zinc content that is particularly beneficial for engines with flat-tappet camshafts, which are found in many vehicles of this era.
Maintenance and Fluid Capacities
Beyond the engine, a comprehensive maintenance schedule for the 735i addresses the transmission, cooling, and braking systems. The automatic transmission, specifically the 4HP-22 model, requires a total fill of 7.9 quarts for a complete change, with an initial fill capacity of 3.2 quarts if the unit has been rebuilt or the torque converter is being serviced. For those opting for manual transmissions in this model, the 260 (5-speed) unit requires 3.4 pints. The cooling system is equally substantial, holding 13.3 quarts of fluid. Ensuring this system is flushed and filled with a high-quality antifreeze like the AMSOIL Passenger Car & Light Truck Antifreeze & Coolant can prevent the thermal shock that often leads to cracked blocks in older engines. The brake system relies on DOT 4 fluid, and switching to a synthetic DOT 3 and DOT 4 AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid ensures that the fluid does not absorb moisture as quickly, maintaining a stable viscosity that provides consistent pedal feel and ABS responsiveness over a wide temperature range.
The differential on the rear axle, designated for GL-5 applications, is another critical component that benefits from synthetic gear lubricants. The capacity for the rear differential is 3.6 pints. Using an appropriate AMSOIL SEVERE GEAR® 80W-90 100% Synthetic Gear Lube helps control thermal runaway and protects against rust and corrosion. These fluids also contain friction modifiers that are beneficial for limited-slip differentials, ensuring that the vehicle handles corners smoothly and without chatter. The use of these specialized fluids extends the life of the gears and bearings, addressing common issues of wear that arise in high-mileage luxury sedans. Proper lubrication of the transfer case, if equipped, is also vital for long-term drivetrain health.
About the Vehicle
The 1987 BMW 735i represents the peak of the E23 generation, a chassis that established the modern luxury sedan benchmark. Introduced in the early 1980s, the E23 was the first BMW to feature a turbocharged engine in the 7 Series, though the 735i model specifically relied on the naturally aspirated, fuel-injected M30 inline-six engine. This engine code, M30 B35, denotes a 3.5-liter displacement that produced a robust 189 horsepower, a figure that was impressive for the time and delivered with a characteristic linear power curve. The car was designed with a focus on grand touring, offering a blend of sporty handling and high-speed stability that appealed to drivers who wanted more than just a comfortable ride. The interior was luxurious for its era, featuring leather upholstery, wood trim, and advanced amenities like an optional four-speed automatic transmission that provided smooth acceleration without the need for manual shifting.
Owners of the 735i typically value the vehicle for its engineering quality and the tactile connection it offers to the road. The steering is precise, the suspension is composed, and the sound of the engine is a distinct, resonant V-like hum that many enthusiasts consider a hallmark of BMW’s driving character. The platform originated in Munich, Germany, and was positioned as a flagship luxury vehicle to compete with other European and American sedans. While it is a heavy vehicle by modern standards, the weight is distributed in a way that aids balance, making it a favorite among drivers who appreciate mechanical sympathy and build quality. It is a sedan that has stood the test of time, with many examples still finding their way onto roads today, often cherished by collectors and driving enthusiasts alike.
Common Issues and Solutions
Despite its robust design, the 1987 735i does have specific vulnerabilities that can affect its long-term reliability. One of the most prevalent issues involves the engine’s oil consumption and seal hardening. As the rubber seals age, they can harden and shrink, leading to leaks that drip oil onto the ground and cause the engine to burn oil. Using a synthetic motor oil with better seal conditioning properties, such as the AMSOIL Extended-Life formula, can help rejuvenate these seals and slow down the rate of oil loss, ensuring the engine remains adequately lubricated between changes.
Another common challenge is the failure of the cooling system components, particularly the plastic thermostat housings and radiators, which can become brittle over time. This can lead to coolant leaks or overheating, which is catastrophic for an older engine. By flushing the system and using a premium antifreeze like the AMSOIL Propylene Glycol Antifreeze, owners can protect the cooling system metals and hoses from corrosion, reducing the risk of sudden failure. Additionally, the transmission fluid in these vehicles often degrades, leading to shuddering or rough shifts. Synthetic transmission fluids resist the breakdown caused by high temperatures and heavy use, maintaining the fluid’s viscosity and preventing the formation of harmful sludge that can clog valves and cause transmission wear.
A final notable problem is the degradation of the brake fluid, which is hygroscopic and absorbs moisture over time. This lowers the boiling point of the fluid, which can lead to brake fade under heavy use and corrosion within the brake lines. Regularly flushing the system with a synthetic brake fluid ensures that the fluid remains dry and stable, providing consistent braking performance. Addressing these four key areas—seal conditioning, cooling system integrity, transmission fluid stability, and brake fluid quality—through the use of high-quality synthetic lubricants is the most effective way to preserve the driving dynamics and reliability of this classic German sedan.
Maintaining a 1987 BMW 735i is a labor of love that rewards the owner with years of reliable performance. By selecting the right lubricants, you are not just following a checklist; you are actively participating in the preservation of automotive history. The specific needs of the M30 engine and the E23 chassis call for premium synthetic fluids that can handle the rigors of daily driving and the unique demands of a vehicle that is decades old. From the initial oil change using the correct viscosity and filter, to the complete fluid replacement in the transmission and cooling system, each step contributes to the overall health of the car. The investment in quality lubricants pays dividends in reduced wear, better performance, and a driving experience that remains engaging and smooth.