Maintaining your 2004 Infiniti FX45 with a high-performance engine requires more than just changing fluids on a schedule; it requires selecting the right formulations to match the unique demands of the 4.5L V8 powerplant. This luxury crossover SUV, powered by the VK45DE engine, relies on precise lubrication to handle its specific operating temperatures and internal clearances. Using the wrong oil or fluid can lead to premature wear, reduced fuel economy, and a decline in the vehicle’s celebrated driving dynamics. Proper lubrication ensures that critical components like the piston rings, valve train, and turbochargers (if equipped with specific upgrades) receive the necessary protection against sludge, wear, and thermal breakdown. For an engine designed to deliver smooth, powerful acceleration, the choice of lubricant directly impacts longevity and performance.
Recommended AMSOIL Products
- AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil – Offers unsurpassed engine protection for up to 25,000 miles or one year, with 75% more protection against horsepower loss and wear.
- AMSOIL Extended-Life 5W-30 100% Synthetic Motor Oil – Provides up to 20,000 miles of protection with 37% more cleaning power to keep the engine running smoother and longer.
- AMSOIL OE 5W-30 100% Synthetic Motor Oil – A high-mileage friendly option that fights sludge and deposits while meeting OEM standards for performance and durability.
- AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil – Specially formulated for vehicles over 75,000 miles to boost cleaning power and reduce sludge by 67%.
- AMSOIL Oil Filter – Delivers 99% filtration efficiency at 20 microns and allows for lower restriction to keep engine parts properly lubricated.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – An ethylene glycol 50/50 pre-mix that provides protection for up to 150,000 miles or 5 years and is compatible with all other coolant colors.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated formulation for extended protection up to 150,000 miles or 5 years in passenger cars and light trucks.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Designed 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 – A fuel-efficient fluid that protects against wear and promotes smooth, shudder-free shifts.
- AMSOIL SEVERE GEAR® 80W-90 100% Synthetic Gear Lube – Provides advanced protection against wear and thermal runaway, ideal for GL-5 applications above 0°C.
- AMSOIL SEVERE GEAR® 75W-90 100% Synthetic Gear Lube – A versatile synthetic gear lube suitable for all temperatures and GL-5 applications, containing friction modifiers for limited-slip differentials.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Delivers excellent ABS and traction-control responsiveness with stable viscosity over a wide temperature range.
- AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid – Formulated to reduce friction and help seals remain soft to prevent leaks while offering high-temperature protection.
Engine Oil and Filtration for the VK45DE
The heart of the 2004 Infiniti FX45 is the 4.5-liter V8 engine, identified as the VK45DE. This naturally aspirated V8 is engineered for smooth power delivery and durability, requiring a lubricant that can handle the heat generated during spirited driving or towing. The recommended viscosity for this engine is SAE 5W-30, which offers the best protection across all temperatures. The system capacity for a standard oil change, including the filter replacement, is 6.8 quarts. Always verify the oil level with the dipstick after the refill and ensure the drain plug is torqued to the specified 25 ft/lbs to prevent leaks.
When it comes to choosing the right motor oil, AMSOIL provides a range of options tailored to the condition of your vehicle and your driving habits. For those seeking the absolute maximum protection, AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil stands out. It is formulated to provide 75% more engine protection against horsepower loss and wear compared to conventional oils. With guaranteed protection for up to 25,000 miles or one year, this fluid is ideal for drivers who want to minimize maintenance visits while maximizing engine longevity. It also outperforms industry standards, keeping the engine clean and running smoothly for longer periods.
If you prefer a balance between performance and cost, or you drive the vehicle in varied conditions without extreme demands, the AMSOIL Extended-Life 5W-30 100% Synthetic Motor Oil is an excellent choice. It offers up to 20,000 miles of guaranteed protection and contains 37% more cleaning power than standard synthetic oils. This added cleaning capability helps remove contaminants and keeps the engine running smoother, which is particularly beneficial for a high-mileage V8 engine. For owners looking for a cost-effective solution that meets OEM standards, the AMSOIL OE 5W-30 100% Synthetic Motor Oil provides robust protection against sludge and deposits while being API licensed.
Should your FX45 have accumulated over 75,000 miles, the high-mileage formula becomes even more critical. The AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil features a unique chemistry designed to address the specific needs of aging engines. It includes boosted detergents and dispersants to clean out deposits, enhanced anti-wear additives to protect critical surfaces, and reduced sludge by 67%. This fluid helps restore performance and extend the life of the engine, ensuring that the V8 continues to run efficiently.
A critical component of any oil change is the filter. A high-quality filter ensures that the oil remains clean by trapping contaminants that can cause wear. The AMSOIL Oil Filter is designed to provide a filtering efficiency of 99 percent at 20 microns. It offers lower restriction compared to many competitors, allowing for better oil flow and lubrication of engine parts. Additionally, it has a greater capacity for trapping small, wear-causing contaminants, which helps reduce engine wear over time and supports the extended service intervals possible with AMSOIL synthetic oils. For those who prefer the reliability of a well-known brand, the WIX Oil Filter is also available, offering premium media that outperforms original equipment manufacturer-branded filters.
Transmission and Drivetrain Lubrication
The 2004 Infiniti FX45 is equipped with a 5-speed automatic transmission, model RE5R05A. This transmission requires a fluid capable of handling the demands of a powerful V8 engine while maintaining smooth shifting characteristics. The total fill capacity for the automatic transmission is 10.9 quarts. Ensuring the correct fluid is used is vital for preventing wear, sludge buildup, and temperature-related issues that can lead to costly repairs.
For optimal performance and protection, AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is the top recommendation. This fluid is engineered to withstand the rigors of heavy towing, elevated temperatures, and challenging terrain. It remains fluid even in sub-zero temperatures, ensuring that your transmission shifts smoothly regardless of the weather. It also provides reserve protection during heavy use, making it ideal for drivers who push their vehicle to its limits.
If you are looking for a fuel-efficient option that offers reliable performance, the AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is a strong alternative. It protects against wear and promotes smooth, shudder-free shifts, ensuring that the 5-speed automatic operates as intended. For applications requiring a multi-vehicle fluid, the AMSOIL Signature Series Multi-Vehicle 100% Synthetic Automatic Transmission Fluid or the AMSOIL OE Multi-Vehicle 100% Synthetic Automatic Transmission Fluid are also viable options, providing robust protection and resistance to sludge buildup.
Cooling, Differential, and Brake Systems
Maintaining the correct temperature is essential for the longevity of any engine. The cooling system for the FX45 holds a capacity of 10.6 quarts. AMSOIL Passenger Car & Light Truck Antifreeze & Coolant is a unique poly-organic acid (OAT) formulation that provides protection for up to 150,000 miles or five years. It is a 50/50 pre-mix that protects all cooling system metals, gaskets, and hoses, and is compatible with all other antifreeze colors. For those who prefer a concentrated formula, the AMSOIL Propylene Glycol Antifreeze and Engine Coolant offers even greater protection against corrosion and erosion, suitable for extended service intervals.
The drivetrain of the FX45 includes a transfer case and differentials that require specific lubricants. For the transfer case, which holds 2.5 pints, and the front differential with a capacity of 1.4 pints, or the rear differential with 3 pints, AMSOIL SEVERE GEAR® 80W-90 100% Synthetic Gear Lube is a recommended choice for temperatures above 0°C. For all-temperature protection, the AMSOIL SEVERE GEAR® 75W-90 100% Synthetic Gear Lube is highly effective. It contains friction modifiers for limited-slip applications and controls thermal runaway to protect against rust and corrosion. For extreme conditions or specific requirements, the AMSOIL SEVERE GEAR® 75W-110 100% Synthetic Gear Lube provides additional protection.
Safety is paramount, and the braking system must perform reliably in all conditions. The FX45 utilizes a hydraulic brake system that requires DOT 3 fluid. AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid offers excellent responsiveness for ABS and traction control systems. It maintains stable viscosity over a wide temperature range, ensuring consistent pedal feel and braking performance. For the power steering system, which requires a specific fluid to maintain seals and reduce friction, AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid is the ideal choice, offering high-temperature protection and low-temperature performance.
About the Vehicle
The 2004 Infiniti FX45 represents a significant milestone in the brand’s history, marking the introduction of the FX series as Infiniti’s first sport crossover. This vehicle bridged the gap between the refined luxury of a sedan and the versatility of an SUV, offering a driving experience that was previously unseen in the crossover segment. Powered by the 4.5-liter V8 engine, the FX45 delivers robust acceleration and a smooth, powerful ride that resonates with enthusiasts who value performance alongside practicality.
Based on the Nissan Skyline platform, the FX45 shares its engineering roots with other high-performance vehicles of the era, ensuring a chassis that is both rigid and responsive. The interior is designed with a focus on driver-centric controls and premium materials, creating a cockpit that feels more like a sports car than a traditional utility vehicle. Owners of the FX45 often cite the vehicle’s balanced handling, powerful engine response, and luxurious appointments as the key reasons for their satisfaction. The V8 engine, with its distinctive sound and linear power delivery, provides ample torque for highway merging and overtaking, making it a favorite for those who enjoy spirited driving.
The FX45’s design also emphasizes safety and comfort, featuring advanced safety systems for its time and a quiet, refined cabin that isolates occupants from road noise. Its all-wheel-drive capability, when equipped, provides confidence in various weather conditions, further enhancing its appeal as a year-round companion. The blend of Japanese engineering, luxury finishes, and dynamic performance has secured the FX45 a loyal following among Infiniti owners who appreciate a vehicle that does not compromise on style or substance.