The 2003 Infiniti Q45 with its 4.5L 8-cylinder VK45DE engine is a sophisticated machine designed for smooth, powerful driving. To maintain the precision engineering and longevity of this luxury sedan, utilizing high-quality synthetic lubricants is essential. AMSOIL provides a complete suite of fluid solutions tailored specifically for the operating conditions and maintenance requirements of the Q45, ensuring optimal protection against wear, heat, and corrosion.
Recommended AMSOIL Products
- AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil – Offers unsurpassed engine protection for up to 25,000 miles, delivering 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 enhanced cleaning power to help keep the engine running smoother for longer.
- AMSOIL OE 5W-30 100% Synthetic Motor Oil – A cost-effective choice that fights sludge and deposits, outperforming conventional oils for OEM mileage protection.
- AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil – Specifically formulated for engines with over 75,000 miles, featuring boosted detergents and reduced sludge by 67%.
- AMSOIL Oil Filter – Delivers 99% filtering efficiency at 20 microns with greater capacity for contaminants than competing filters.
- WIX Oil Filter – A premium aftermarket alternative that offers improvements over original equipment manufacturer-branded filters.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A unique poly-organic acid formulation that protects cooling system metals, gaskets, and hoses for up to 150,000 miles.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated option that greatly surpasses standards for metallic corrosion and erosion protection.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Withstands heavy towing, elevated temperatures, and challenging terrain while remaining fluid in sub-zero conditions.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Provides essential wear protection for automatic transmissions in a fuel-efficient formulation.
- AMSOIL SEVERE GEAR® 80W-90 100% Synthetic Gear Lube – Features advanced protection against wear, rust, and corrosion for GL-5 rear differentials.
- AMSOIL SEVERE GEAR® 75W-90 100% Synthetic Gear Lube – Controls thermal runaway and helps reduce operating temperatures for extended oil, seal, and equipment life.
- AMSOIL SEVERE GEAR® 75W-110 100% Synthetic Gear Lube – An additional viscosity option for limited-slip applications requiring robust protection.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Ensures excellent ABS and traction-control responsiveness with stable viscosity over a wide temperature range.
- AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid – Reduces friction and keeps seals soft to prevent leaks while resisting heat for long fluid life.
- AMSOIL P.i. Performance Improver Gasoline Additive – Restores up to 14% horsepower and cleans GDI fuel injectors to 100% flow rate after one tank of fuel.
- AMSOIL Gasoline Stabilizer – Keeps fuel fresh for up to 12 months, protecting against varnish and gum buildup.
- WIX Cabin Air Filters – Premium media offers improvements over original equipment manufacturer-branded filters.
Engine Oil Selection and Capacities
The heart of the 2003 Infiniti Q45 is the VK45DE, a 4.5-liter naturally aspirated V8 engine. This powerplant is renowned for its smooth operation and durability, but like any high-performance engine, it demands premium lubrication to sustain its longevity. For this vehicle, AMSOIL recommends a viscosity of 5W-30 for all temperature conditions. This grade is preferred to ensure proper flow during cold starts and stable protection at high operating temperatures. The total oil capacity, including the filter change, is 5.9 quarts. When topping off or changing the oil, always ensure the drain plug is torqued to the correct specification of 22-29 ft/lbs, and check the oil level after the refill.
The AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil is the ultimate choice for owners seeking the maximum possible protection. It is engineered to provide up to 25,000 miles of service, offering significant advantages over standard conventional oils regarding wear protection and horsepower preservation. If your driving involves more frequent stop-and-go traffic or slightly shorter trip distances, the AMSOIL Extended-Life 5W-30 100% Synthetic Motor Oil offers a robust alternative with up to 20,000 miles of guaranteed protection and superior cleaning power to maintain engine efficiency. For those looking for an economical solution that still delivers 100% synthetic benefits, the AMSOIL OE 5W-30 100% Synthetic Motor Oil is an excellent option that effectively fights sludge and deposits. Additionally, for Q45 models with substantial mileage exceeding 75,000 miles, the AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil is formulated with enhanced anti-wear additives and detergents to reduce sludge and help the engine perform better.
Pairing your motor oil with a high-quality filter is critical for removing contaminants. The AMSOIL Oil Filter is designed with greater capacity for small, wear-causing contaminants and offers extended service life to match the oil intervals. Alternatively, the WIX Oil Filter provides premium media that improves upon OEM standards, making it a reliable choice for routine maintenance.
Transmission and Differential Fluids
The 2003 Infiniti Q45 is equipped with an automatic transmission, specifically the RE5R05A model. Proper lubrication here is vital to prevent sludge buildup, wear, and temperature-related issues that can lead to costly repairs. The total fill capacity for the automatic transmission is 10.9 quarts. AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is designed to withstand the rigors of heavy towing, elevated temperatures, and challenging terrain, remaining fluid even in sub-zero conditions. The AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is another strong option that provides essential protection against wear while maintaining fuel efficiency.
For the rear differential, which requires a GL-5 compatible lubricant, AMSOIL SEVERE GEAR 80W-90 100% Synthetic Gear Lube and AMSOIL SEVERE GEAR 75W-90 100% Synthetic Gear Lube offer advanced protection. These variants provide control against thermal runaway and rust while helping to reduce operating temperatures. The AMSOIL SEVERE GEAR 75W-110 100% Synthetic Gear Lube is also available for specific limited-slip applications. The capacity for the rear differential is 3 pints. Using a high-quality synthetic gear lube ensures long oil life, seal life, and equipment life, while containing friction modifiers for limited-slip applications.
Coolant, Brake, and Power Steering Fluids
Cooling system maintenance is essential for the VK45DE engine. The system holds 10.4 quarts of AMSOIL Passenger Car & Light Truck Antifreeze & Coolant. This unique poly-organic acid (OAT) formulation protects all cooling system metals, gaskets, and hoses for up to 150,000 miles or 5 years. It is phosphate-, nitrate-, nitrite-, silicate-, borate-, and amine-free, making it compatible with all other antifreeze colors. For those who prefer a concentrated option that requires mixing with distilled water, the AMSOIL Propylene Glycol Antifreeze and Engine Coolant offers protection up to 150,000 miles and significantly surpasses standards for metallic corrosion and erosion.
Brake safety should never be compromised. The 2003 Infiniti Q45 requires a DOT 3 hydraulic AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid. This fluid provides excellent ABS and traction-control responsiveness, maintaining stable viscosity over a wide temperature range. For the power steering system, AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid is recommended. It reduces friction, helps seals remain soft to prevent leaks, and resists heat for a long fluid life, ensuring quiet operation and excellent high- and low-temperature performance.
Additional Maintenance Products
To maximize the performance and fuel economy of the Infiniti Q45, AMSOIL offers the AMSOIL P.i. Performance Improver Gasoline Additive. This formula restores up to 14% horsepower and cleans GDI fuel injectors to 100% flow rate after just one tank of treated fuel, helping to prevent carbon rap and control pre-ignition knock. It is compatible with capless fuel systems and can reduce the need for costly higher-octane fuel. For seasonal storage, AMSOIL Gasoline Stabilizer helps keep fuel fresh for up to 12 months, protecting against varnish and gum buildup while fighting ethanol corrosion. For winterization or protection of external components, AMSOIL Engine Fogging Oil provides a highly effective rust preventive for internal engine components during storage or long periods of inactivity.
About the Vehicle
The 2003 Infiniti Q45 represents the pinnacle of Infiniti’s luxury sedan lineup during the early 2000s. Built on the F platform, it shares engineering DNA with the Nissan Fuga but is distinctly tuned for the American luxury market. This vehicle is powered by the robust 4.5-liter VK45DE V8 engine, a naturally aspirated powerplant that delivers smooth, linear power rather than aggressive turbocharged bursts. Owners of the Q45 often praise its exceptionally smooth ride quality, quiet cabin, and the high level of interior craftsmanship, which features extensive wood trim and soft-touch materials typical of the era’s premium Japanese vehicles.
The Q45 was positioned as a competitor to the Cadillac DTS and the Lexus LS430. Its reputation is built on reliability and durability, making it a favorite among long-distance drivers and fleet managers. The chassis tuning provides a balanced blend of comfort and sporty handling, allowing the heavy sedan to navigate corners with surprising agility. While it lacks the forced induction found in many of its contemporaries, the naturally aspirated V8 is known for its longevity, provided it receives consistent maintenance.
However, as with any vehicle that has seen significant mileage, the Q45 can develop specific issues. One common challenge for the VK45DE engine is oil consumption, which can increase as the engine ages due to the deterioration of piston rings and valve stem seals. Regular use of high-quality synthetic oil helps mitigate this by maintaining better sealing properties and reducing sludge buildup that can exacerbate consumption. Another potential problem is the failure of the coolant pump, which can lead to overheating if not addressed promptly. Using a high-performance antifreeze like AMSOIL’s can help extend the life of cooling components and prevent corrosion.
Owners may also encounter issues with the power steering pump noise, often caused by fluid degradation and seal hardening over time. Switching to a synthetic power steering fluid can restore quiet operation and protect the pump’s internal components. Finally, transmission shift quality can degrade if the fluid becomes contaminated with clutch material and heat-treated debris. An automatic transmission fluid flush with a premium synthetic fluid can restore smooth shifting and prevent premature wear on the transmission bands and clutches. By addressing these common areas with the right lubricants, Q45 owners can keep their vehicle performing at a near-factory level for many more miles.