The heart of your 2008 GL550 is the 5.5L V8 engine, which requires a lubricant that can handle high loads and high heat. The factory recommended oil viscosity ranges from 0W-20 to 0W-40 for all temperatures, and 5W-30 or 5W-40 for temperatures above -25°C. However, for a vehicle of this caliber and age, switching to a premium full synthetic is the best way to ensure protection. The engine oil capacity is 9.5 quarts when the filter is included. After refilling, it is critical to check the oil level to ensure the proper amount is used.
AMSOIL 5W-40 FS 100% Synthetic European Motor Oil is an excellent choice for this vehicle. Designed specifically for the unique demands of European gasoline and diesel vehicles, this oil features a precise blend of synthetic base oils and premium additives. It offers extended service intervals and superior wear protection compared to conventional oils. For drivers in colder climates or those who prefer maximum flow during cold starts, the AMSOIL 0W-40 FS 100% Synthetic European Motor Oil is also a top-tier option. Both oils provide exceptional thermal stability and oxidation resistance, keeping the engine clean and reducing wear on critical components like camshafts and pistons.
Filtration and Oil Change Kits
Even the best motor oil will eventually lose its effectiveness if contaminants are not removed from the system. For the GL550, the AMSOIL Oil Filter (Code EA15K39-EA) is a highly effective choice. This filter provides a filtering efficiency of 99 percent at 20 microns, which is crucial for capturing the microscopic particles that cause engine wear. It is built with high-capacity media to hold more contaminants than many competing filters, helping to reduce engine wear and allow for extended service intervals.
For those who prefer established aftermarket brands, the WIX Oil Filter (Code 57078-EA) is also available. It features premium media that offers improvements over original equipment manufacturer-branded filters. Owners of the GL550 can choose between an oil change kit featuring the AMSOIL Oil Filter or one with the WIX Oil Filter, depending on their specific maintenance preferences. Using the correct filter ensures that your investment in premium synthetic oil is protected by a filtration system designed to maximize clean oil flow.
Transmission and Transfer Case Lubrication
The automatic transmission in the 2008 GL550, specifically the 722.9 series, requires a fluid that can handle the rigors of a heavy luxury SUV. Whether your vehicle has the reduced-friction code (A89) or not, proper fluid is vital for smooth shifting and longevity. The total fill capacity for the 7-speed 722.9 transmission is 9.5 quarts.
AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is engineered for this application. It remains fluid in sub-zero temperatures while providing the necessary resistance to shear and thermal breakdown during heavy towing or challenging terrain. This fluid helps reduce friction and protects against wear, sludge, and temperature-related problems. For those seeking a more cost-effective option that still meets OE specifications, the AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is a reliable alternative that protects against wear and maintains transmission health.
For the transfer case, the requirements vary based on the specific configuration (Code 430). If your vehicle is equipped with Code 430, the capacity is 3.2 pints, while models without this code require 1.1 pints. In these applications, the same AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid can often be used effectively to lubricate the gears and bearings, ensuring smooth operation in all-weather conditions.
Cooling System Maintenance
Keeping the engine at the correct operating temperature is just as important as lubrication. The cooling system for the 2008 GL550 holds 12.7 quarts of coolant. Using the wrong coolant can lead to corrosion, gasket failure, and costly overheating issues. AMSOIL Passenger Car & Light Truck Antifreeze & Coolant is a phosphate-, nitrate-, nitrite-, silicate-, borate-, and amine-free formulation that is compatible with all other antifreeze colors. It provides protection for up to 150,000 miles or 5 years.
For those who prefer a concentrated antifreeze that requires mixing with distilled water, the AMSOIL Propylene Glycol Antifreeze and Engine Coolant is an outstanding choice. This product greatly surpasses standards for metallic corrosion and erosion. It offers protection for up to 150,000 miles in passenger cars and light trucks, or significantly longer in heavy-duty applications. Both options are ethylene glycol-free (in the propylene glycol version) or formulated to be compatible, ensuring safe operation for all cooling system metals, gaskets, and hoses.
Additional Care and Fuel System Health
Maintaining a 2008 Mercedes-Benz GL550 involves more than just changing fluids. The fuel system plays a critical role in engine performance, especially as vehicles accumulate miles. The AMSOIL P.i.® Performance Improver Gasoline Additive is a powerful treatment that can help restore up to 14% horsepower and clean fuel injectors. It works to remove carbon buildup and control pre-ignition knock, ensuring your V8 engine runs smoothly and efficiently.
For long-term storage, AMSOIL Gasoline Stabilizer helps keep fuel fresh for up to 12 months, protecting against varnish and gum buildup caused by ethanol corrosion. Additionally, the AMSOIL Engine Fogging Oil is highly effective at preventing rust inside the engine cylinders during long periods of inactivity. For exterior and interior maintenance, products like the AMSOIL Miracle Wash Waterless Wash and Wax Spray and the AMSOIL Silicone Spray can help keep your vehicle looking pristine and protect rubber components from cracking and drying out. These additives and protectants work together to ensure the GL550 remains a reliable and impressive driver for years to come.
Why Proper Lubrication Matters for This Vehicle
Proper lubrication is the difference between a GL550 that runs smoothly and one that suffers premature wear. The high-compression 5.5L V8 generates significant heat and internal pressure. Without high-quality synthetic lubricants, the oil film can break down, leading to increased friction, deposit formation, and potential engine damage. By using AMSOIL synthetic oils and filters, owners can significantly reduce engine wear, improve fuel economy, and extend the service life of critical components. This level of protection is essential for a vehicle that is driven in varying conditions, from city commuting to highway towing.
About the Vehicle
The 2008 Mercedes-Benz GL550 represents a peak in the brand’s lineup of luxury SUVs, blending the rugged capability of an off-road vehicle with the plush comfort expected of a high-end German automobile. Built on the robust M-CLASS platform, the GL550 is powered by the legendary M273 5.5-liter V8 engine, a pushrod design known for its smooth power delivery and reliability. This engine produces substantial torque, making the vehicle a capable hauler for towing and a smooth cruiser on the open highway.
Equipped with a sophisticated 7-speed automatic transmission and a robust 4MATIC four-wheel-drive system, the GL550 is engineered to handle diverse terrains while maintaining a refined ride quality. The interior typically features high-quality leather, advanced technology for its time, and spacious seating for passengers, making it a favorite among families and executives alike. The vehicle’s stance is commanding, with a design that emphasizes both utility and elegance. Owners often appreciate the GL550 for its versatility, as it serves equally well for daily commuting, family road trips, and more demanding outdoor adventures. Its reputation for durability and its status as a luxury icon make regular maintenance with premium synthetic fluids essential to preserve its value and performance over the long term.