The 2009 Mercedes-Benz S550 is a vehicle defined by its blend of high-performance luxury and engineering precision. Under the hood lies the impressive 5.5-liter V8 engine, known for delivering substantial horsepower while maintaining the smooth, refined driving character that the S-Class is famous for. However, this sophisticated powerplant places specific demands on its lubrication systems that standard petroleum oils often fail to meet consistently over the long term. For owners seeking to maximize engine life, maintain optimal performance, and ensure the smooth operation of the transmission and hydraulic systems, selecting the correct synthetic fluids is critical. Proper lubrication not only protects against wear during extreme temperatures but also helps manage the high heat and stress generated by this powerful V8.
Recommended AMSOIL Products
- AMSOIL 5W-40 FS 100% Synthetic European Motor Oil – Specifically engineered for the precise demands of European vehicles, this oil features a unique blend of synthetic base oils and premium additives designed to provide superior protection against high-temperature wear and sludge formation.
- AMSOIL 0W-40 FS 100% Synthetic European Motor Oil – An excellent alternative for drivers who require maximum cold-temperature flow for quick lubrication at startup, offering the same high-temperature stability and wear protection as the 5W-40 variant.
- AMSOIL Oil Filter – This high-efficiency filter provides 99 percent filtration at 20 microns, capturing small, wear-causing contaminants more effectively than many competing filters to help extend the life of your engine.
- WIX Oil Filter – A premium alternative offering improvements over original equipment manufacturer (OEM)-branded filters with high-quality media for reliable protection.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A poly-organic acid (OAT) formulation that protects cooling system metals, gaskets, and hoses while offering corrosion protection for up to 150,000 miles or 5 years.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated option providing protection up to 150,000 miles, ideal for those who prefer mixing their own coolant solutions.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Designed to withstand the rigors of heavy towing and elevated temperatures, this fluid remains fluid in sub-zero conditions and provides reserve protection during intense use.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – A cost-effective option that meets original equipment manufacturer standards for vehicles without specific reduced-friction requirements.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Provides excellent responsiveness for ABS and traction control systems, with a stable viscosity that ensures consistent pedal feel across a wide temperature range.
- AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid – Designed for quiet operation with strong anti-wear protection and excellent temperature performance to keep seals soft and prevent leaks.
Engine Oil and Filtration for the 5.5L V8
The heart of the 2009 S550 is the 5.5-liter M273 V8 engine. This power unit requires a lubricant that can handle significant thermal stress while protecting precision-engineered components. The engine oil capacity for this vehicle is 9.0 quarts when the filter is changed. For optimal performance, owners have two primary viscosity choices depending on their climate and driving style. AMSOIL recommends either the 5W-40 FS 100% Synthetic European Motor Oil or the 0W-40 FS 100% Synthetic European Motor Oil. Both formulas are designed with a European-specific additive package that ensures the oil meets the stringent requirements of Mercedes-Benz engines, providing a robust film strength that standard oils may lack.
The choice between the 5W-40 and 0W-40 often comes down to ambient temperature preferences. The 0W-40 offers superior flow in extremely cold conditions, ensuring immediate oil pressure upon startup, while the 5W-40 provides excellent balance for a wide range of temperatures. Whichever viscosity is chosen, filtration is paramount. The AMSOIL Oil Filter is recommended to ensure that the synthetic oil remains clean. This filter offers a filtration efficiency of 99 percent at 20 microns, which is crucial for removing microscopic contaminants that can cause wear on camshafts, bearings, and cylinder walls over time.
Transmission and Differential Protection
The automatic transmission in the 2009 S550 is a complex hydraulic system that benefits greatly from a high-quality synthetic fluid. Whether your vehicle has the 7-speed 4MATIC system or other variants, maintaining the correct fluid properties is essential for shift quality and longevity. The total fill capacity for a 7-speed 4MATIC transmission (722.9) is approximately 10.1 quarts. It is vital to note that for units with the A89 code (Reduced-Friction), specific fluid formulations are required to maintain proper friction characteristics.
For this transmission, the AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is a top-tier choice. This fluid is engineered to withstand heavy towing, elevated temperatures, and challenging terrain without losing its viscosity or protective qualities. It remains fluid in sub-zero temperatures and provides a reserve of protection during heavy use, making it ideal for the spirited driving that many S550 owners enjoy. The alternative, the AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid, also offers excellent protection against wear while meeting original equipment manufacturer standards for vehicles without the specific reduced-friction code.
If the vehicle is equipped with a transfer case, the Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is also recommended for this application. This versatility ensures that all lubrication needs for the drivetrain are met with high-performance synthetic fluid that resists shear and thermal breakdown, extending the life of the differential and transfer case components.
Brake Fluid and Power Steering
Safety and control are paramount in a luxury sedan like the S-Class. The braking system of the 2009 S550 requires a fluid that not only transmits pedal force effectively but also withstands the heat generated during braking. The recommended fluid meets DOT 3 and DOT 4 specifications, and AMSOIL offers a 100% Synthetic Brake Fluid that exceeds these standards. This fluid offers excellent ABS and traction-control responsiveness, ensuring that the vehicle’s sophisticated safety systems function reliably. It maintains a stable viscosity over a wide temperature range, preventing the boiling points from dropping during intense driving sessions.
For the power steering system, the 2009 S550 requires a fluid that keeps seals soft to prevent leaks while reducing friction for smooth operation. The AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid is designed for quiet operation and offers strong anti-wear protection. Its excellent high-temperature and low-temperature performance ensures that steering remains responsive in both freezing winters and hot summers, helping to prevent leaks and extend the life of the steering pump and seals.
Coolant System Maintenance
The cooling system in the 2009 S550 is critical for managing the heat of the V8 engine. Depending on the specific configuration, particularly regarding rear air conditioning, the coolant capacity varies. With rear AC, the system holds 13.8 quarts, while a model without rear AC requires 12.2 quarts. Using a high-quality antifreeze is essential to protect the engine block, radiator, and heater core from corrosion and freezing.
AMSOIL offers two primary options for this application. The Passenger Car & Light Truck Antifreeze & Coolant is a 50/50 pre-mix formulation that requires no additional water and is compatible with all other coolant colors. It protects all cooling system metals, gaskets, and hoses. For those preferring a concentrated option, the AMSOIL Propylene Glycol Antifreeze and Engine Coolant offers protection up to 150,000 miles or 5 years and is compatible with a wide range of vehicle types. Both formulations are free of phosphates, nitrates, nitrites, silicates, borates, and amines, ensuring compatibility with the materials used in Mercedes-Benz cooling systems.
Fuel System Care and Storage
Maintaining the fuel system of a direct-injection V8 engine involves more than just filling the tank. Carbon buildup can reduce power and fuel economy over time. The AMSOIL P.i.® Performance Improver Gasoline Additive is recommended to restore up to 14% horsepower and clean fuel injectors to 100% flow rate after just one tank of fuel. This additive helps prevent carbon rap and controls pre-ignition knock, ensuring the engine runs smoothly and efficiently.
For seasonal storage, the vehicle may require specific preparations to prevent fuel degradation and internal engine corrosion. The AMSOIL Gasoline Stabilizer helps keep fuel fresh for up to 12 months, protecting against varnish and gum buildup while fighting ethanol corrosion. Additionally, the AMSOIL Engine Fogging Oil is a highly effective rust preventive designed to protect internal engine components during long periods of inactivity, ideal for storing the S550 during winter months or extended vacations.
About the Vehicle
The 2009 Mercedes-Benz S550 represents a significant chapter in the history of the S-Class sedan, marking the transition period where the 5.5-liter naturally aspirated V8 was the primary powerplant for the S550 model. Part of the W221 generation, which was produced from 2005 to 2013, this era of the S-Class is widely celebrated for its balance of traditional luxury and emerging technology. The S550 was introduced as a successor to the S500, offering improved performance and efficiency through the refinement of the M273 engine family. This engine, known for its code 273.968, delivers a robust blend of power and smoothness, typical of the German engineering excellence associated with the brand.
Owners of the 2009 S550 often appreciate its sophisticated driving dynamics, which include the optional 4MATIC all-wheel-drive system available on the 722.9 transmission. The vehicle was positioned as a flagship luxury sedan, competing directly with other high-end European sedans. Its reputation is built on a foundation of comfort, safety, and reliability, making it a popular choice for those who value a commanding presence on the road without sacrificing ride quality. The S550’s design language features the classic long-wheelbase proportions of the S-Class, offering a spacious interior that serves as a mobile sanctuary. While it may not possess the extreme horsepower figures of the later AMG models, the S550’s V8 provides ample power for confident passing and highway cruising. The build quality of the W221 chassis is renowned for its rigidity and acoustic isolation, ensuring a quiet and composed ride even when pushing the vehicle’s limits. This makes it a vehicle that rewards responsible driving with consistent performance and a driving experience that blends sportiness with ultimate comfort.