Maintaining the high-performance 3.0L turbocharged inline-six engine of your 2018 BMW 640i requires more than just following a standard service interval. This sophisticated powerplant, identified by the engine code N55B30A, operates under significant thermal and mechanical stress. The turbocharger spins at incredibly high speeds, generating heat that can degrade conventional oils rapidly, while the engine’s precise tolerances demand a fluid that maintains its viscosity and protective film strength under all conditions. Using the correct lubricants ensures that critical components like the turbo bearings, variable valve timing mechanisms, and the VVTi system receive consistent lubrication, preventing costly wear and maintaining the vehicle’s renowned driving dynamics.
Recommended AMSOIL Products
- AMSOIL 0W-30 MS 100% Synthetic European Motor Oil – A specialized synthetic formula designed specifically for the unique demands of European gasoline, diesel, and hybrid vehicles, offering superior protection against sludge and wear.
- AMSOIL Oil Filter – Provides 99% filtration efficiency at 20 microns, offering greater capacity for contaminants than competing filters to help reduce engine wear.
- MANN-FILTERS Oil Filter – A premium alternative featuring media that offers improvements over original equipment manufacturer branded filters.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A phosphate, nitrate, and silicate-free pre-mix that protects cooling system metals, gaskets, and hoses while exceeding OEM requirements.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated formula that requires mixing with water, offering extended protection up to 150,000 miles or 5 years.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Engineered to withstand heavy towing, elevated temperatures, and challenging terrain while remaining fluid in sub-zero conditions.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Provides reliable protection against wear for automatic transmissions, including the GA8HP45Z used in this model.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Delivers excellent ABS and traction-control responsiveness with a stable viscosity over a wide temperature range.
Engine Oil and Filtration for the N55B30A
The heart of your 2018 BMW 640i is the N55B30A engine, a single-turbocharged 3.0-liter inline-six. This powerplant is known for its smooth power delivery and robust torque, but the high boost pressures place immense stress on the engine’s internal components. To combat this, AMSOIL recommends the 0W-30 MS 100% Synthetic European Motor Oil. This fluid is engineered with a precise blend of synthetic base oils and premium additives specifically formulated for the tight tolerances of European engines. It helps control the higher oil consumption that can sometimes occur in turbocharged BMW engines while providing superior shear stability to maintain film strength under load.
The oil capacity for this vehicle is 6.9 quarts when performing a complete change with a filter replacement. It is crucial to remember to check the oil level after the refill, as the electronic dipstick or the visual gauge requires the engine to be at the correct operating temperature and level on a flat surface. The drain plug torque specification is 18 ft/lbs, and replacing the drain plug seal during every service is a best practice to prevent future leaks. To ensure that the newly added oil remains clean, pairing the oil with the AMSOIL Oil Filter is highly recommended. This filter features synthetic media that offers higher filtration efficiency than standard paper filters, capturing smaller wear-causing particles that can damage the turbocharger bearings and the timing chain tensioners. An alternative option is the MANN-FILTERS Oil Filter, which also provides premium media performance comparable to the OEM standard.
Transmission and Cooling System Care
The 2018 BMW 640i is equipped with the ZF 8HP (specifically the GA8HP45Z) 8-speed automatic transmission. This sophisticated gearbox requires a fluid that can handle rapid shifts and the heat generated during spirited driving. Using a high-quality synthetic transmission fluid is essential for maintaining shift quality and preventing premature wear of clutch packs and solenoids. The Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is designed to meet the strict demands of these German transmissions. It offers resistance to thermal breakdown and oxidation, ensuring the fluid maintains its viscosity and lubricity even during heavy towing or aggressive driving. If you prefer a cost-effective solution that still delivers full synthetic performance, the AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is an excellent choice that meets or exceeds the necessary OEM specifications. A full fluid change for the 8-speed transmission requires approximately 9 quarts.
Cooling is equally critical for the 640i, as the turbocharged engine generates significant heat. The cooling system capacity is 10.8 quarts. Maintaining the correct antifreeze-to-water ratio is vital for preventing corrosion, boiling over in summer, and freezing in winter. The AMSOIL Passenger Car & Light Truck Antifreeze & Coolant comes as a 50/50 pre-mix, making it convenient to use. It is formulated to be compatible with all cooling system metals, gaskets, and hoses while being free of phosphates, nitrates, and silicates that can damage seals over time. For those who prefer mixing their own, the AMSOIL Propylene Glycol Antifreeze and Engine Coolant provides maximum flexibility and extended service intervals, protecting the engine for up to 5 years or 150,000 miles.
Brake Fluid and Fluid Maintenance
BMW vehicles rely heavily on their braking systems for safety and handling. The factory recommends a specific low-viscosity DOT 4 fluid, often identified by BMW part numbers 83 13 0 443 024 or 83 13 0 443 026. Over time, brake fluid absorbs moisture from the atmosphere, which lowers its boiling point and can lead to brake fade or corrosion in the ABS module. To resolve this, the AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid is an ideal replacement. Its synthetic formulation ensures a high dry and wet boiling point, providing consistent pedal feel and preventing vapor lock. The stable viscosity also ensures excellent responsiveness for traction control and ABS systems, which are integral to the 640i’s all-wheel-drive dynamics and safety systems.
Why Owners Like This Vehicle and Common Challenges
The 2018 BMW 640i represents the pinnacle of the F12/F13 generation of the BMW 6 Series, a lineage that blends luxurious grand touring comfort with genuine sports car performance. Known for its elegant, sloping roofline and refined interior, the 640i offers a driving experience that feels both exclusive and incredibly capable. The heart of the car, the N55 engine, replaced the older twin-turbo setup with a more efficient single-turbo design that still delivers strong torque from low RPMs, making daily driving effortless while reserving power for when needed. Enthusiasts appreciate the car’s balanced chassis, rear-wheel-drive bias (often with xDrive), and the iconic BMW steering feel that makes every corner an engaging experience. It sits comfortably in the market as a premium grand tourer, appealing to drivers who value performance and prestige without the ultra-luxury price tag of the 7 Series or the 8 Series.
However, like many high-performance European vehicles, the 640i has specific areas that benefit from diligent maintenance. One common issue in this engine family is carbon buildup on the intake valves, a characteristic of direct injection engines. Regular use of a high-quality fuel system cleaner can help mitigate this accumulation, preserving fuel economy and engine smoothness over the vehicle’s life. Another concern involves the plastic cooling system components, which can become brittle over time due to thermal cycling; using a corrosion-inhibiting coolant like the AMSOIL antifreeze formulations can help extend the life of these plastic hoses and seals. Owners often report that the engine can consume oil, particularly if driven in a performance-oriented manner or at high speeds; the synthetic 0W-30 MS oil is specifically designed to handle these higher consumption rates while protecting the turbocharger and valve train. Finally, the transmission solenoids and mechatronic units can sometimes be sensitive to fluid quality; sticking to a high-performance synthetic transmission fluid ensures that the complex hydraulic systems within the ZF 8HP transmission operate smoothly for years to come.
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