Maintaining the 2009 Mercedes Benz CLK350 3.5L requires precise fluid specifications to ensure the 3.5L V6 engine runs smoothly and delivers the performance Mercedes drivers expect. Proper lubrication is critical for this vehicle, as the engine and transmission are engineered to handle high-stress conditions, from spirited driving on winding roads to daily highway commuting. Using fluids that meet or exceed the manufacturer’s stringent standards helps prevent premature wear, maintains fuel efficiency, and ensures the longevity of critical components. Whether you are driving in extreme heat or cold, selecting the right synthetic oils and coolants provides a protective barrier that conventional fluids cannot match.
Recommended AMSOIL Products
- AMSOIL 5W-40 FS 100% Synthetic European Motor Oil – This specialized European formula features a precise blend of synthetic base oils designed specifically for the unique demands of gasoline, diesel, and hybrid vehicles, offering superior protection for the CLK350’s high-stress engine.
- AMSOIL 0W-40 FS 100% Synthetic European Motor Oil – An excellent alternative viscosity for extreme temperature performance, this synthetic European motor oil provides robust protection during cold starts and sustained high-temperature driving conditions.
- AMSOIL Oil Filter – Engineered to work in tandem with synthetic oils, this filter offers 99 percent filtering efficiency at 20 microns and a higher contaminant capacity than competing brands to keep the engine running clean and reduce wear.
- WIX Oil Filter – Premium media offers improvements over original equipment manufacturer (OEM)-branded filters, ensuring optimal flow and filtration for extended service intervals.
- MANN-FILTERS Oil Filter – Premium media offers improvements over original equipment manufacturer (OEM)-branded filters, ensuring optimal flow and filtration for extended service intervals.
- MANN-FILTERS Air Filters – Premium media offers improvements over original equipment manufacturer (OEM)-branded filters, ensuring optimal airflow and filtration for engine longevity.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Designed for the Mercedes 722.9 transmission, this fluid withstands heavy towing and elevated temperatures while remaining fluid in sub-zero conditions to protect against wear and sludge.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – A high-performance alternative that protects against wear and provides the efficiency required for the vehicle’s automatic transmission systems, ensuring smooth shifting and extended service life.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A ready-to-use 50/50 pre-mix formulation that protects all cooling system metals, gaskets, and hoses, offering up to 150,000 miles or 5 years of protection with a phosphate, nitrate, and silicate-free design.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated option that greatly surpasses OEM standards for metallic corrosion and erosion, requiring mixing with distilled water for a protective solution that can last up to 150,000 miles or 5 years.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Provides excellent responsiveness for ABS and traction-control systems, maintaining stable viscosity over a wide temperature range to ensure reliable braking performance in all conditions.
- AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid – Formulated for quiet operation, this fluid helps seals remain soft to prevent leaks while resisting heat for long fluid life and offering strong anti-wear protection for the steering system.
The engine oil capacity for the 2009 Mercedes Benz CLK350 with the 3.5L 6-cylinder engine (Engine Code 3498cc W) is 8.5 quarts when including the filter. It is important to note that on models equipped with an oil cooler, additional oil may be needed if the cooler is drained. Drivers should allow at least five minutes after refilling or turning the engine off before checking the oil level to ensure an accurate reading. The oil drain plug should be torqued to 22 ft/lbs. When selecting a viscosity, AMSOIL recommends the European formula which supports 0W-30, 0W-40 (for all temperatures), and 5W-30, 5W-40 (for temperatures above -25°C). This flexibility allows the vehicle to perform optimally regardless of the ambient climate.
Transmission and Cooling System Maintenance
The automatic transmission in the CLK350 is a critical component that requires precise fluid compatibility. For the Mercedes 722.9 transmission, the total fill capacity is 9.5 quarts. There are two variations depending on the data card code: models without the reduced-friction code A89 and those with the A89 code. In both scenarios, using a high-quality synthetic automatic transmission fluid is essential. AMSOIL’s Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid and OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid are specifically formulated to withstand the rigors of heavy towing, elevated temperatures, and challenging terrain. They remain fluid in sub-zero temperatures, providing reserve protection during heavy use and preventing the wear and sludge buildup that can lead to costly transmission repairs. The fuel-efficient formulation helps maintain power transmission efficiency, contributing to better overall fuel economy.
Equally vital is the cooling system, which manages the heat generated by the powerful V6 engine. The coolant capacity for this vehicle is 7.5 quarts. AMSOIL offers two distinct options to suit different maintenance preferences. The Passenger Car & Light Truck Antifreeze & Coolant is a ready-to-use 50/50 pre-mix formulation made from ethylene glycol. It is engineered to exceed original equipment manufacturer requirements and protects all cooling system metals, gaskets, and hoses. Being free of phosphates, nitrates, nitrites, silicates, borates, and amines, it is safe for a wide variety of vehicle components. For those who prefer a concentrated solution, the AMSOIL Propylene Glycol Antifreeze and Engine Coolant offers superior protection. It greatly surpasses standards for metallic corrosion and erosion and can extend protection up to 150,000 miles or 5 years, whichever comes first. Both options are compatible with all other antifreeze colors and ensure the engine operates within its ideal temperature range.
Essential Fluids for Brakes and Steering
While engine and transmission fluids often get the most attention, the braking and steering systems of a luxury vehicle like the CLK350 require equal care. For the brake system, which utilizes HBH specifications, AMSOIL recommends their DOT 3 and DOT 4 100% Synthetic Brake Fluid. This product provides excellent responsiveness for ABS and traction-control systems, ensuring stable viscosity across a wide temperature range. It is formulated to meet the stringent requirements of MB Sheet 331.0, offering a safe and effective replacement for the factory fluid. Similarly, the power steering system benefits from the AMSOIL 100% Synthetic Multi-Vehicle Power Steering Fluid. Designed for the PS031 specification, this fluid reduces friction and helps keep seals soft to prevent leaks. It resists heat, ensuring a long fluid life, and offers strong anti-wear protection. The formulation is specifically designed for quiet operation, preserving the smooth and silent driving characteristics that owners of the CLK350 appreciate.
About the Vehicle
The 2009 Mercedes-Benz CLK350 represents a blend of luxury, performance, and engineering excellence from the early 2000s. As a compact executive coupe and convertible, it sits in a unique market position between the entry-level C-Class and the larger E-Class, offering a spirited driving experience without sacrificing comfort. Powered by the robust 3.5L V6 engine, often identified as the M272, the CLK350 delivers smooth acceleration and a refined power delivery that is characteristic of the German brand. This engine family is renowned for its reliability and high-revving nature, making it a favorite among enthusiasts who appreciate linear power output and a pleasant exhaust note.
Part of the W209 generation, the CLK350 was designed with a focus on elegance and dynamics. Its sleek, aerodynamic profile and luxurious interior materials create a sophisticated ambiance, while the suspension tuning provides a balanced ride that is responsive yet composed. The vehicle was popular for its versatility, available in both coupe and cabriolet body styles, appealing to those who enjoy open-top motoring. The platform shares lineage with the C-Class sedan but with a distinct personality, emphasizing a sportier stance and a more engaging driving character. Owners typically value this model for its timeless design, which has aged well, and the underlying mechanical durability of the Mercedes engineering. Whether cruising along the coast or navigating city streets, the CLK350 remains a vehicle that offers a commanding presence and a premium driving experience, making proper fluid maintenance a key part of keeping it in top condition.
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