The 2008 Mercedes-Benz GL450 is a robust full-size luxury SUV built on the W164 platform, powered by the reliable 4.7-liter M273 V8 engine. While this vehicle is designed for both on-road comfort and light off-road capability, its complex engineering places high demands on its lubrication systems. Proper maintenance is essential to preserve the vehicle’s performance, fuel economy, and longevity. Using the correct viscosity and specification fluids ensures that critical components like the engine, transmission, and cooling system operate within their designed parameters, preventing premature wear and costly repairs.
Recommended AMSOIL Products
- AMSOIL 5W-40 FS 100% Synthetic European Motor Oil – This premium synthetic oil is formulated specifically for the high-temperature demands and precision tolerances of European gasoline, diesel, and hybrid vehicles, offering superior protection for the GL450’s V8 engine.
- AMSOIL 0W-40 FS 100% Synthetic European Motor Oil – An excellent choice for varying climates, this European formula provides rapid flow at cold starts and stable protection at high operating temperatures, ensuring the engine is lubricated immediately upon startup.
- AMSOIL Oil Filter – Designed to work in tandem with synthetic motor oils, this filter offers 99 percent filtration efficiency at 20 microns and greater capacity for contaminants than standard filters to reduce engine wear.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Ideal for the 722.9 transmission series, this fluid withstands heavy towing and elevated temperatures while maintaining fluidity in sub-zero conditions, ensuring smooth shifts and extended transmission life.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – A high-performance alternative that protects against wear and provides excellent torque converter performance for the GL450’s automatic transmission.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Meets or exceeds Mercedes-Benz specifications for DOT 4 fluids, offering excellent ABS responsiveness and stable viscosity over a wide temperature range for safer braking performance.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – This pre-mixed 50/50 formulation protects the cooling system metals, gaskets, and hoses for up to 150,000 miles or 5 years, preventing overheating and corrosion in the V8 engine.
- AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid – This fluid helps seals remain soft to prevent leaks and resists heat breakdown, ensuring quiet and responsive power steering operation in the GL450.
- MANN-FILTERS Oil Filter – A premium OEM-equivalent filter featuring advanced media technology that outperforms standard filters in capturing small, wear-causing contaminants.
- WIX Oil Filter – Offers premium filtration media with improvements over standard OEM-branded filters, ensuring clean oil circulation and reduced engine wear.
Engine Oil and Filter Specifications
Maintaining the 4.7-liter V8 engine (Engine Code 273.923 9) requires precise fluid selection. The engine demands a specific oil volume to ensure proper lubrication of the crankshaft, camshafts, and valve train. For a complete oil change, the 2008 Mercedes-Benz GL450 requires 9.5 quarts of oil when the filter is replaced. If the vehicle is equipped with an oil cooler, additional oil may be necessary if the cooler is drained during the service. It is crucial to allow at least 5 minutes after refilling or turning the engine off before checking the oil level to ensure an accurate reading on the dipstick. When reinstalling the drain plug, the torque specification is 22 ft/lbs to prevent stripping the threads or causing a leak.
AMSOIL offers two primary viscosity options for this engine, both designed with the unique demands of European vehicles in mind. The 5W-40 FS provides a balanced protection profile for a wide range of driving conditions, utilizing a precise blend of synthetic base oils and premium additives. For drivers operating in colder climates or those seeking faster oil flow at startup, the 0W-40 FS is an excellent choice. Both oils exceed original equipment manufacturer requirements, offering extended service intervals and superior protection against high-temperature breakdown.
Filtration is just as critical as the oil itself. The AMSOIL Oil Filter features a proprietary synthetic media that captures microscopic contaminants, reducing engine wear even more effectively than standard paper filters. For owners who prefer established aftermarket brands, the MANN-FILTERS and WIX Oil Filters are also recommended. These filters utilize premium media technologies that offer improvements over OEM-branded counterparts, ensuring the oil circulates freely while removing harmful particles that can scar engine components.
Transmission and Drivetrain Fluids
The 2008 GL450 is equipped with a sophisticated automatic transmission, typically identified by the Mercedes-Benz type code 722.9. Proper lubrication here is vital for the longevity of the transmission, torque converter, and differential systems. For the 7-speed 722.9 transmission without the reduced-friction code (A89) or with specific data card configurations, a total fill requires 9.5 quarts. This capacity ensures the torque converter and internal valves are fully flooded, which is essential for the transmission’s electronic control systems to function correctly.
AMSOIL provides top-tier options for this application. The Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is engineered to withstand the rigors of heavy towing, elevated temperatures, and challenging terrain. It remains fluid in sub-zero temperatures and provides reserve protection during heavy use. Alternatively, the OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid offers robust protection against wear while maintaining fuel efficiency. Both fluids are designed to last longer than conventional oils, helping to prevent sludge formation and transmission-related failures.
The drivetrain also includes a transfer case and front differential that require specialized lubrication. For the double-speed transfer case, the capacity is 3.2 pints, while the single-speed version requires 1.1 pints. The front differential holds 2.3 pints. In these applications, the Signature Series or OE synthetic automatic transmission fluids can also be utilized for transfer case lubrication, ensuring compatibility and protection for the gears within the 4MATIC all-wheel-drive system.
Cooling, Brake, and Steering Systems
Proper thermal management is critical for the 4.7L V8 engine. The cooling system capacity for the 2008 GL450 is 10.6 quarts. To ensure long-term protection against corrosion and overheating, the AMSOIL Passenger Car & Light Truck Antifreeze & Coolant is a top recommendation. This product features a unique poly-organic acid (OAT) formulation that protects all cooling system metals, gaskets, and hoses. It is a 50/50 pre-mix, phosphate-free, nitrate-free, and silicate-free, making it compatible with all other coolant colors. For those who prefer concentrated solutions that allow for precise mixing ratios, the AMSOIL Propylene Glycol Antifreeze and Engine Coolant offers extended protection up to 150,000 miles or 5 years.
Brake fluid quality directly impacts vehicle safety. The GL450 requires a DOT 4 compatible fluid, often specified as MB Sheet 331.0. The AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid provides excellent ABS and traction-control responsiveness. It maintains stable viscosity over a wide temperature range, which is crucial for preventing brake fade under heavy load or in extreme heat, while resisting moisture absorption that can lower boiling points.
Power steering operation relies on fluid that remains fluid and protective. The AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid is formulated to reduce friction and help seals remain soft to prevent leaks. It offers strong anti-wear protection and excellent high-temperature performance, ensuring the steering system operates quietly and smoothly for the life of the vehicle.
Maintenance and Additional Products
Beyond fluid changes, keeping the GL450 in top condition involves maintaining clean air and fuel systems. The MANN-FILTERS Air Filter ensures that the engine breathes freely, trapping dust and debris before it can enter the combustion chamber. For fuel system health, the AMSOIL P.i. Performance Improver can restore up to 14% horsepower and clean GDI fuel injectors to 100% flow rate. It reduces the need for higher-octane fuel and helps prevent carbon buildup and pre-ignition knock.
For vehicle owners who store their SUVs seasonally, protection against corrosion and fuel degradation is essential. The AMSOIL Gasoline Stabilizer keeps fuel fresh for up to 12 months, preventing varnish and gum buildup. To protect internal engine components during storage, the AMSOIL Engine Fogging Oil is a highly effective rust preventive.
Additional care products like the AMSOIL Brake and Parts Cleaner help remove oil, grease, and brake fluid from components without leaving residue. For exterior maintenance, the AMSOIL Miracle Wash Waterless Wash and Wax Spray provides a fantastic shine and UV protection with just a spray and wipe, while the AMSOIL Exterior Ceramic Spray offers long-lasting water-shedding properties. Interior surfaces can be treated with AMSOIL Interior Detailer – Light Lemon or AMSOIL Interior Detailer – Scent Free to trap odors and provide UV protection for up to 90 days.
Vehicle Background
When Mercedes-Benz launched the GL-Class in 2006, they introduced the W164 platform, a bold statement in the luxury SUV market. By 2008, the GL450 had firmly established itself as a competitor to the Cadillac Escalade and the Lincoln Navigator, but with a distinct European engineering pedigree. The vehicle was designed to bridge the gap between a sporty crossover and a full-size body-on-frame SUV, offering a unibody construction that provided a smoother, more car-like ride while retaining the rugged capability expected from the brand. The 4.7-liter M273 V8 engine was the heart of the GL450, known for its smooth power delivery and robust torque output, making it well-suited for towing and hauling heavy loads across varied terrain.
The GL450 was also notable for its advanced 4MATIC all-wheel-drive system, which distributed power dynamically between the front and rear axles to ensure stability and traction in both wet and off-road conditions. Owners of this model often appreciate its blend of luxury amenities and practical utility, making it a favorite for families and adventurers alike. The interior space is generous, accommodating up to seven passengers with comfortable seating, while the cargo area remains substantial even with all seats in use. Over the years, the 2008 model has developed a reputation for reliability, provided it receives consistent maintenance, particularly regarding its complex transmission and cooling systems. Its design philosophy emphasized a balance of performance and comfort, ensuring that the GL450 remains a desirable vehicle for those who demand the best from their German engineering.