Maintaining the 2009 Mercedes-Benz CLS550 with its powerful 5.5-liter V8 engine requires more than just a standard oil change; it demands specialized fluids engineered to meet the precise tolerances of German automotive technology. This vehicle, equipped with the high-strung engine code 273.960 S, operates under significant thermal and mechanical stress. Using lubricants that exceed the original equipment manufacturer standards is essential to preserve horsepower, protect against wear in the high-rpm engine, and ensure the longevity of the transmission. Whether you are navigating city traffic or pushing the vehicle on the open road, the right fluid chemistry provides a vital buffer against sludge, oxidation, and temperature extremes.
Recommended AMSOIL Products
- AMSOIL 5W-40 FS 100% Synthetic European Motor Oil – A specialized formula designed specifically for the unique demands of European gasoline, diesel, and hybrid vehicles, offering exceptional protection at both high and low temperatures.
- AMSOIL 0W-40 FS 100% Synthetic European Motor Oil – An ultra-versatile European-grade oil that provides superior cold-start protection and thermal stability for extended service intervals.
- AMSOIL Oil Filter – Engineered to provide 99% filtration efficiency at 20 microns, this filter traps small contaminants that cause wear and extends the life of your motor oil.
- WIX Oil Filter – A premium alternative featuring advanced media that offers improvements over standard OEM-branded filters for reliable contaminant control.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Built to withstand the rigors of heavy towing, elevated temperatures, and challenging terrain while maintaining fluidity in sub-zero conditions.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – A high-performance synthetic designed to protect the transmission against wear and friction for smooth shifting.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A phosphate-, nitrate-, nitrite-, silicate-, borate-, and amine-free 50/50 pre-mix formulation that protects all cooling system metals and lasts up to 150,000 miles.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated option that greatly surpasses corrosion standards, requiring mixing with distilled water for ultimate cooling system protection.
Engine Oil and Filtration
The heart of the 2009 Mercedes-Benz CLS550 is its 5.5-liter V8 engine, which requires a lubricant that can handle high output and precise clearances. AMSOIL recommends a total oil capacity of 9.0 quarts when including the filter change. The engine specifications call for viscosities of 0W-20, 0W-30, or 0W-40 for all temperatures, with 5W-30 and 5W-40 suitable for temperatures above -25°C. To meet these rigorous European standards, the AMSOIL 5W-40 FS 100% Synthetic European Motor Oil is an ideal choice. This oil features a precise blend of synthetic base oils and premium additives specifically formulated for the high-performance gasoline and diesel engines found in Mercedes-Benz vehicles. It provides the necessary film strength to protect camshafts, bearings, and turbochargers under the highest loads. For those seeking maximum cold-weather flow and extended drain intervals, the AMSOIL 0W-40 FS 100% Synthetic European Motor Oil is an excellent alternative that delivers comparable protection with superior cold-start characteristics.
Protection is equally dependent on filtration. The engine oil is only as good as the filter that contains the contaminants it removes. The AMSOIL Oil Filter is designed to trap 99% of contaminants at 20 microns, significantly better than many standard filters. This higher efficiency allows for lower flow restriction, keeping engine parts lubricated and reducing the wear caused by small particles that slip past lesser media. For a more traditional OEM-style swap, the WIX Oil Filter offers premium media that improves upon original equipment manufacturer filtration, ensuring that sludge and soot do not accumulate in the oil galleries.
Transmission Fluid for the 722.9 System
The power generated by the 5.5-liter engine is managed by a sophisticated automatic transmission, likely a 722.9 model (without code A89 Reduced Friction on the datacard). Maintaining this transmission is critical for the vehicle’s drivability and efficiency. The total fill capacity for a 9-speed 722.9 transmission is approximately 9.7 quarts. Conventional fluids often degrade under the heat and friction of a vehicle with this level of power, leading to sluggish shifts and premature wear. The AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is engineered to withstand the specific rigors of this transmission. It remains fluid in sub-zero temperatures and provides a reserve of protection during heavy use, such as towing or spirited driving, ensuring that the transmission shifts smoothly even under extreme conditions.
For owners who prefer a fluid that closely mimics original equipment specifications while still offering the superior protection of synthetic technology, the AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid is an excellent choice. It is designed to protect against wear and friction, extending the life of the transmission bands and clutches. By using these synthetic fluids, owners can help prevent the sludge and temperature-related problems that often plague high-mileage transmissions, ensuring the 2009 CLS550 remains a reliable and responsive vehicle.
Cooling System Maintenance
A healthy cooling system is paramount for a high-compression V8 engine. The 2009 Mercedes-Benz CLS550 has a coolant capacity of 11.9 quarts. The cooling system must protect against corrosion, freezing, and boiling while managing the immense heat generated by the engine. The AMSOIL Passenger Car & Light Truck Antifreeze & Coolant is a unique poly-organic acid (OAT) formulation that is phosphate-, nitrate-, nitrite-, silicate-, borate-, and amine-free. This “silicate-free” chemistry is crucial for preventing damage to the aluminum components often found in modern cooling systems. Pre-mixed at a 50/50 ratio with water, it offers protection for up to 150,000 miles or five years. For those who prefer a concentrated solution that can be mixed to specific ratios for different climates, the AMSOIL Propylene Glycol Antifreeze and Engine Coolant provides a robust option. It greatly surpasses standards for metallic corrosion and erosion, making it an ideal choice for maintaining the cooling system’s integrity over the long term.
Vehicle Background
Model History and Performance
The 2009 Mercedes-Benz CLS550 represents a distinct chapter in automotive history, blending the sleek, four-door coupe aesthetic with the power of a high-performance sedan. Introduced to the market as a “four-door sports car,” the CLS-Class (C219 generation) was Mercedes-Benz’s answer to a niche that was largely empty at the time. The 5.5-liter M273 V8 engine in the CLS550 is a masterpiece of engineering, delivering roughly 429 horsepower and a substantial amount of torque. This powertrain, combined with the 7-speed automatic transmission (722.9), provides a driving experience that is both exhilarating and refined. The vehicle’s low-slung, fastback roofline, reminiscent of the iconic 300 SL Gullwing, gave it a timeless appeal that set it apart from the more boxy luxury sedans of the era.
Owners of the 2009 CLS550 often cite the vehicle’s commanding road presence and smooth power delivery as its defining characteristics. The M273 engine is known for its broad powerband and responsive throttle, making it equally suitable for daily commuting or weekend canyon runs. The car’s suspension tuning offers a balance between comfort and sporty handling, allowing the heavy vehicle to corner with surprising agility. Built in Sindelfingen, Germany, this model is part of Mercedes-Benz’s long tradition of combining luxury with performance. The CLS550’s reputation as a sophisticated grand tourer makes it a favorite among enthusiasts who value both style and substance. Its unique design language has aged well, continuing to turn heads even nearly two decades after its release. Understanding the engineering intent behind this vehicle helps explain why it requires premium, specialized lubricants to maintain its performance and character for years to come.