The heart of the 2018 BMW X4 is the N55B30A 3.0L turbocharged inline-six engine. This powerplant operates with tight tolerances and generates significant heat, particularly from the turbocharger. The recommended oil grade for this engine is 0W-30, which flows freely at startup to protect critical components during cold weather while maintaining film strength at operating temperatures. The total fluid capacity, including the oil filter replacement, is 6.9 quarts.
When performing an oil change, it is essential to torque the oil drain plug to 18 ft-lbs and replace the drain plug seal to prevent leaks. Using the correct filter is equally important. The AMSOIL Oil Filter is designed to work in harmony with the AMSOIL 0W-30 MS European Motor Oil. This filter media provides a high efficiency rating, capturing small wear-causing particles that standard filters might miss, thereby reducing engine wear and maintaining oil cleanliness for longer periods. For owners who prefer OEM-style filtration, the MANN-FILTERS Oil Filter is also a recommended alternative, offering premium media that exceeds the performance of many factory-installed units.
Transmission and Differential Protection
The 2018 BMW X4 typically features an 8-speed automatic transmission (GA8HP45Z). These transmissions are sensitive to fluid degradation and heat buildup. While a total fill requires 9 quarts for a complete flush, top-offs and partial fills should utilize the same high-quality synthetic fluid. The AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is optimized for these applications, offering protection against the heat and stress of stop-and-go traffic and spirited driving. It remains fluid in extreme cold and provides reserve protection during heavy use.
For those seeking an OE-specified alternative, the AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid provides comparable protection and fuel efficiency. In the transfer case and differential, the X4 utilizes lubricants for its all-wheel-drive system. While specific fluid recommendations for the front differential were not listed in the primary capacity data, the use of high-quality synthetic gear lubes is generally advised for maintaining the longevity of the drive train components.
Cooling and Brake Systems
Maintaining the cooling system is vital for the longevity of the turbocharger and the engine itself. The cooling system capacity for the 2018 BMW X4 is 10.1 quarts. Owners have two excellent choices for coolant: the AMSOIL Passenger Car & Light Truck Antifreeze & Coolant, which comes pre-mixed and is ready to use, or the AMSOIL Propylene Glycol Antifreeze and Engine Coolant for those who prefer mixing their own for maximum control and extended intervals up to 150,000 miles. Both formulations are phosphate-, nitrate-, and silicate-free, ensuring compatibility with the various metals and rubber hoses found in modern BMW cooling systems.
The braking system of the X4 requires a fluid that resists boiling under hard braking and provides crisp pedal feel. The AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid is a superior choice, offering a high boiling point and stable viscosity. This fluid ensures excellent responsiveness from the ABS and traction control systems, which are critical for the vehicle’s dynamic handling characteristics.
About the Vehicle: 2018 BMW X4
The 2018 BMW X4 occupies a unique space in the automotive market, bridging the gap between the practicality of an SUV and the sportiness of a coupe. Part of BMW’s “X4” model line, which sits alongside the X3, the X4 is often described as a “Sports Activity Coupe.” It is built on the same platform as the BMW X3, sharing its fundamental architecture and driving dynamics, but with a distinctively sloping roofline that tapers toward the rear, giving it a sleek, aggressive profile.
Equipped with the N55B30A engine, the 3.0L inline-six delivers robust performance. The N55 engine is a turbocharged unit that replaced the twin-turbo N54 in many BMW applications, streamlining the design while maintaining high power output and responsiveness. This engine is known for its smooth power delivery and is a staple in BMW’s performance lineup. The 2018 X4 typically comes paired with an 8-speed automatic transmission, which is highly regarded for its quick shift times and ability to manage the torque of the inline-six effectively. The vehicle features BMW’s xDrive all-wheel-drive system, providing excellent traction in various weather conditions without sacrificing the car’s athletic handling.
Owners of the 2018 BMW X4 generally appreciate the blend of luxury, performance, and utility. The interior is designed with a driver-centric layout, featuring high-quality materials and advanced technology interfaces common to the BMW brand. The X4 appeals to drivers who want the elevated seating position and cargo space of an SUV but refuse to compromise on the road feel of a sports car. It is a vehicle that handles corners with confidence and offers a refined ride quality on highways.
Despite its reliability, the 2018 BMW X4, like many modern performance vehicles, can benefit from proactive maintenance to address specific known issues. One common concern with the N55 engine is carbon buildup on the intake valves due to direct injection technology. While the engine design has improved over earlier generations, the accumulation of carbon can eventually affect performance and fuel economy. Using a high-quality fuel additive like AMSOIL P.i. Performance Improver can help maintain injector cleanliness and reduce carbon deposits, helping to restore lost horsepower and improve throttle response.
Another potential area of concern for owners is the cooling system’s susceptibility to leaks and overheating, particularly as the vehicle ages. The N55 engine runs at high temperatures, and the plastic components in the cooling system can become brittle over time. Regularly flushing the system with a high-performance coolant like AMSOIL Antifreeze can help prevent corrosion and erosion of metal components, extending the life of the water pump and thermostat housing. Additionally, the turbocharger relies on a constant flow of clean oil and proper cooling; using a synthetic oil that resists thermal breakdown and a coolant that effectively manages heat can mitigate the risk of turbo-related failures.
Tire wear and suspension component wear are also considerations for any high-performance vehicle. The sport-tuned suspension of the X4 provides a firm, engaging ride, but it can lead to faster wear on certain bushings and mounts. While the lubrication guidelines focus on fluids, ensuring the chassis is clean and protected from road grime and salt using products like AMSOIL Synthetic Multi-Purpose Grease or AMSOIL Heavy-Duty Metal Protector can help prevent premature corrosion of suspension bolts and undercarriage components, keeping the vehicle’s handling sharp and reliable for years to come.
Ultimately, the 2018 BMW X4 is a sophisticated machine that rewards attentive care. By selecting lubricants and fluids that exceed OEM specifications, owners can ensure that the vehicle continues to deliver the spirited driving experience and luxurious comfort it was designed for, while minimizing the risk of common wear-related issues associated with high-performance turbocharged engines.