The 2018 Mercedes-Benz GLS63 AMG is a formidable full-size luxury SUV that combines immense performance with everyday utility. Under the hood lies a potent 5.5-liter twin-turbocharged V8 engine, engineered to deliver dynamic power while navigating the demands of a heavy vehicle platform. To ensure this sophisticated machine continues to perform at its peak, it requires lubricants specifically designed to meet the rigorous tolerances and thermal stresses of European engineering. Standard fluids often lack the necessary stability to protect complex components like the twin-turbos, high-pressure fuel systems, and precision-matched transmissions. Switching to premium AMSOIL 5W-40 FS motor oils provides a significant advantage, offering superior thermal resistance, reduced oil consumption, and extended service intervals that align with the vehicle’s high-performance nature.
Recommended AMSOIL Products
- AMSOIL 5W-40 FS 100% Synthetic European Motor Oil – Engineered for the unique demands of high-performance European vehicles, featuring a precise blend of synthetic base oils and premium additives to handle extreme heat and turbocharger stress.
- AMSOIL 0W-40 FS 100% Synthetic European Motor Oil – Provides superior cold-weather starting fluidity while maintaining a strong protective film at operating temperatures, ideal for the GLS63’s twin-turbo V8.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A phosphate, nitrite, nitrate, borate, silicate, and amine-free formulation that offers protection for up to 150,000 miles or five years, safeguarding all cooling system metals and gaskets.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated coolant that greatly surpasses OEM standards for corrosion and erosion protection, extending service life to 150,000 miles or five years in passenger cars.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Withstands the rigors of heavy towing and elevated temperatures, remaining fluid in sub-zero conditions to protect the 7-speed transmission’s delicate hydraulics.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Designed to match OE specifications for wear protection and fuel efficiency, ensuring smooth shifts and extended transmission life.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Delivers excellent ABS and traction-control responsiveness with a stable viscosity across a wide temperature range, ensuring consistent braking performance.
Maintaining the 2018 Mercedes-Benz GLS63 AMG requires attention to specific fluid capacities and change intervals that differ from standard vehicles. The engine, a robust 5.5-liter 8-cylinder unit (Engine Code 157.98.6 Turbo), holds 9 quarts of oil when a filter change is included. Owners should note that after refilling, the oil level must be checked, and the oil drain plug torque specifications are critical: M12 bolts require 15 ft/lbs, M14 bolts require 22 ft/lbs, and plastic plugs should be torqued to 3 ft/lbs to prevent leaks or stripped threads. The cooling system also has specific needs; the high-temperature cooling circuit (HTCC) requires 8.5 quarts, while the low-temperature cooling circuit (LTCC) requires 2 quarts. Using AMSOIL Propylene Glycol Antifreeze and Engine Coolant in these circuits ensures that the complex network of radiators, intercoolers, and engine passages remains free of corrosive deposits that can lead to overheating or premature failure.
Transmission and Differential Protection
The automatic transmission in the GLS63 AMG, specifically the 722.9 series, operates under immense stress due to the vehicle’s high horsepower and torque output. Depending on whether the vehicle has the A89 code for reduced friction, the total fill capacity for a 7-speed 722.9 transmission is 9.5 quarts. Standard fluids can break down under the thermal load of aggressive driving or towing, leading to sluggish shifts and increased wear. AMSOIL Signature Series Fuel-Efficient and OE Fuel-Efficient fluids are formulated to maintain viscosity and lubricity under these conditions. They provide a protective film that reduces friction, which not only extends the life of the clutch packs and bands but also contributes to better fuel economy. For the transfer case, lubrication is equally vital to ensure power is distributed effectively across all four wheels, particularly in adverse weather or off-road conditions where the GLS63 excels.
Brake System and Fluid Maintenance
Safety is paramount in a vehicle of this size and speed. The braking system on the GLS63 AMG requires a fluid that can withstand the high temperatures generated during hard stops without boiling. The factory specification calls for DOT 4 plus or products approved on Mercedes-Benz Sheet 331.0. AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid meets and exceeds these requirements. It offers a stable viscosity that ensures crisp pedal feel in both freezing and scorching conditions. This synthetic fluid also resists moisture absorption better than conventional glycol-based fluids, which helps prevent internal corrosion of the brake lines and calipers. Regular fluid flushes are essential to maintain optimal braking performance and prevent the “spongy” feel that can occur when moisture content rises.
The comprehensive suite of AMSOIL P.i.® Performance Improver gasoline additives further enhances the maintenance regimen for the GLS63 AMG. For fuel system care, the AMSOIL P.i. Performance Improver gasoline additive can restore up to 14% horsepower and restore GDI fuel injectors to 100% flow rate, counteracting the carbon buildup common in direct injection engines. Additionally, the AMSOIL Upper Cylinder Lubricant Corrosion Inhibitor helps lubricate the fuel system and upper cylinders, providing an extra layer of protection against wear. For seasonal storage, the AMSOIL Gasoline Stabilizer keeps fuel fresh for up to 12 months, protecting against varnish and ethanol corrosion, while the AMSOIL Engine Fogging Oil coats internal components to prevent rust during periods of inactivity. These products work together to ensure that every aspect of the vehicle’s operation is optimized, from cold starts to high-speed cruising.
About the Vehicle
The 2018 Mercedes-Benz GLS63 AMG represents the pinnacle of the luxury SUV segment, effectively redefining what a “full-size” vehicle can be. Based on the Mercedes-Benz GL-Class platform, the GLS63 AMG is a high-performance variant that serves as the brand’s flagship luxury SUV. It is widely regarded as a “four-door supercar” that offers the practicality of a family hauler with the raw power and handling dynamics typically reserved for sports sedans. This model is powered by the M157 5.5-liter V8 twin-turbocharged engine, a unit renowned for its ability to generate over 500 horsepower and massive torque figures. This engine is mated to a 7G-Tronic PLUS 7-speed automatic transmission with an AMG Speedshift MCT manual mode, delivering seamless power delivery and rapid acceleration that can propel the heavy SUV to 60 mph in roughly four seconds.
Originating from Germany, Mercedes-Benz has built a reputation for engineering excellence and durability. The GLS class is designed to accommodate up to seven passengers comfortably, featuring a spacious cabin, premium leather upholstery, and advanced technology suites that include driver assistance systems and a luxurious infotainment setup. Owners often appreciate the vehicle’s commanding road presence and its ability to glide over rough terrain with surprising agility, thanks to its adaptive air suspension and 4MATIC all-wheel-drive system. The GLS63 AMG, in particular, attracts enthusiasts who value the blend of speed, comfort, and utility, making it a favorite for those who need a daily driver that can also tow trailers or handle spirited driving on weekends.
Despite its robust engineering, the GLS63 AMG can face certain maintenance challenges common to high-performance German vehicles. One prevalent issue is carbon buildup on the intake valves, which can occur due to the direct injection system used in the M157 engine. Over time, this buildup can lead to rough idling, reduced fuel efficiency, and a loss of power. Regular use of fuel system cleaners like AMSOIL P.i. can help mitigate this issue by cleaning injectors and preventing deposit formation. Another area of concern is the oil consumption rate, which can sometimes be higher in these high-output engines. Using a high-quality synthetic oil formulated for European vehicles, such as the AMSOIL 5W-40 FS line, provides the necessary volatility control and film strength to minimize consumption and extend oil life. Additionally, owners should be vigilant about brake fluid quality, as the intense heat generated during performance driving can cause conventional brake fluids to degrade or absorb moisture, leading to reduced braking efficiency and potential corrosion in the brake lines.
A fourth common concern for these high-mileage vehicles is the potential for transmission wear due to the heavy loads and high torque levels the drivetrain must manage. The 722.9 transmission is sophisticated but benefits greatly from a fluid that maintains its frictional properties over a long period. Using AMSOIL Signature Series fuel-efficient transmission fluids helps preserve the clutch packs and ensure smooth gear changes, even as the vehicle accumulates significant mileage. Finally, cooling system health is critical for any twin-turbo engine, as overheating can lead to catastrophic failure. Ensuring that the AMSOIL Propylene Glycol Antifreeze and Engine Coolant is fresh and free of contaminants helps maintain optimal operating temperatures, protecting the engine and intercooler components from thermal stress. By addressing these specific needs with high-performance lubricants, GLS63 owners can maintain the vehicle’s legendary status for reliability and performance.