The 2018 Cadillac CTS with the 3.6L LGX S engine demands lubricants that can withstand the high operating temperatures and mechanical stress associated with its direct-injection design. Using the correct synthetic fluids is essential to maintaining the vehicle’s performance, ensuring the turbocharger stays cool, and preventing premature engine wear caused by sludge or deposit buildup. AMSOIL offers a comprehensive line of products specifically formulated to exceed the GM dexos1 Gen 3 specifications required for this engine, providing superior protection against horsepower loss and LSPI (Low-Speed Pre-Ignition).
Recommended AMSOIL Products
Selecting the right lubricant begins with identifying the specific fluid requirements for the 2018 Cadillac CTS. Below are the premier AMSOIL products recommended for this vehicle, including the optimal motor oil, oil filter, and essential maintenance fluids.
- AMSOIL Signature Series 5W-30 100% Synthetic Motor Oil – Delivers the highest level of engine protection with 75% more resistance against horsepower loss and wear, capable of protecting the turbocharger 72% better than the required GM specification.
- AMSOIL Extended-Life 5W-30 100% Synthetic Motor Oil – Offers 37% more cleaning power to keep the engine running smoother for up to 20,000 miles of protection.
- AMSOIL OE 5W-30 100% Synthetic Motor Oil – A cost-effective option that fights sludge and deposits, featuring zero LSPI events in testing required by GM dexos1 Gen 2 standards.
- AMSOIL 5W-30 100% Synthetic High-Mileage Motor Oil – Formulated with unique chemistry for vehicles with over 75,000 miles to boost detergency and reduce sludge by 67%.
- AMSOIL Oil Filter – Provides 99% filtering efficiency at 20 microns and allows for lower restriction to keep engine parts lubricated while reducing wear.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Withstands heavy towing, elevated temperatures, and sub-zero conditions while providing reserve protection during abuse.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – A fuel-efficient alternative that protects against transmission wear for those seeking OEM-equivalent performance.
- AMSOIL SEVERE GEAR® 75W-90 100% Synthetic Gear Lube – Advanced protection for front standard and limited-slip differentials, controlling thermal runaway and rust.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A pre-mixed, phosphate and silicate-free formulation that protects cooling system metals and lasts up to 150,000 miles.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated formulation that exceeds corrosion standards and offers extended service intervals.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Provides excellent ABS responsiveness and stable viscosity over a wide temperature range, meeting GM P/N 19353126 requirements.
Why Proper Lubrication Matters for the 3.6L LGX Engine
The 3.6L LGX engine found in the 2018 Cadillac CTS is a sophisticated direct-injection powerplant that operates at high temperatures. The stress on the engine components is significant, particularly in the turbocharger area. Using a standard conventional oil or even a generic synthetic may not provide the necessary thermal stability or anti-wear additives required to prevent breakdown under extreme load. AMSOIL motor oils are engineered with base stocks and additive packages that resist oxidation and thermal shear, ensuring the oil maintains its viscosity and protective properties even when the engine is pushed to its limits. This is crucial for preventing oil consumption issues and extending the life of the variable valve timing system.
Complete Lubrication Guide
To ensure the longevity of your 2018 Cadillac CTS, a comprehensive fluid maintenance approach is recommended. This involves more than just the engine oil; the cooling, transmission, and differential systems all require specific attention.
Engine Oil and Filter Capacity
For the 3.6L 6-cylinder engine (Code [S] LGX S), the oil capacity is 6.6 quarts when the oil filter is replaced. If the filter is not replaced, the capacity is slightly lower at 6.0 quarts. It is critical to fill to the correct level and check the oil level after the refill. The torque specification for the oil drain plug is 18 ft/lbs. The factory specification has been updated from Dexos 1 Gen 2 to GM Dexos 1 Gen 3, which AMSOIL Signature Series, Extended-Life, and OE oils all exceed. The AMSOIL Oil Filter (EAO17) is the recommended companion, ensuring that contaminants are captured efficiently without restricting flow.
Transmission Fluid and Differential Lubes
The CTS relies on a robust transmission system that can benefit from AMSOIL’s synthetic fluid formulations. For the 8L45 transmission, the total fill capacity is 10.9 quarts, and with a cooler, it rises to 11.4 quarts. Initial fill is 7.4 quarts. Using a synthetic transmission fluid like the Signature Series Fuel-Efficient Automatic Transmission Fluid ensures the transmission remains fluid in sub-zero temperatures and resists the thermal breakdown that occurs during heavy towing or spirited driving.
In the rear differential, specific applications dictate the fluid choice. For the front standard differential (SL146), the capacity is 0.8 pints. For the rear differential, the requirements vary by component. The ELSD clutch requires a specific fluid, with a capacity of 0.2 pints, while the standard rear differential with a 195mm setup holds 1.9 pints. For limited-slip differentials, AMSOIL SEVERE GEAR 75W-90 is ideal, containing friction modifiers designed for these applications to prevent chatter and ensure smooth operation.
Antifreeze and Brake Fluid
The cooling system for the 3.6L engine holds a significant volume of fluid. With the engine block cooler, the capacity is 11.2 quarts, and without it, 10.6 quarts. AMSOIL Passenger Car & Light Truck Antifreeze is a pre-mix formula that is compatible with all other coolant colors and protects against corrosion without the use of harmful silicates or phosphates. For braking performance, AMSOIL DOT 3 and DOT 4 Synthetic Brake Fluid ensures consistent pedal feel and high boiling points, crucial for maintaining safety in stop-and-go city driving or on winding roads.
Vehicle Background
The 2018 Cadillac CTS represents the peak of Cadillac’s midsize luxury sedan lineup during that era. Part of the third generation (produced from 2014 to 2019), the CTS was designed to compete directly with the BMW 5 Series and Mercedes-Benz E-Class, aiming to provide a driving dynamics experience that rivaled its European competitors while offering American luxury and technology. Powered by the LGX engine, this particular variant features a naturally aspirated 3.6-liter V6 that delivers a smooth and powerful output, characterized by responsive throttle and refined acceleration. The LGX engine is part of GM’s High Feature V6 family, known for its aluminum construction, direct injection, and variable valve timing, making it a sophisticated piece of engineering that rewards regular maintenance with high-performance reliability.
Owners of the 2018 CTS typically appreciate its balanced chassis tuning, which offers a sporty yet comfortable ride. The interior is widely praised for its high-quality materials, intuitive infotainment system, and supportive seating, making it a popular choice for daily commuters who also enjoy weekend drives. The vehicle’s reputation is built on its ability to blend luxury with a driver-focused character, often cited as one of the best-handling sedans in its class.
However, like any complex modern vehicle, the 2018 CTS has known issues that can affect long-term ownership. One common problem is oil consumption or leaks around the valve cover gaskets and oil filter housing, which can be exacerbated by the high heat generated by the turbocharger and direct injection system. Using a high-quality synthetic motor oil with enhanced sealing properties can help mitigate these leaks and reduce consumption. Another frequent issue involves carbon buildup on the intake valves due to direct injection, which can lead to rough idling and loss of power; AMSOIL P.i. Performance Improver is an excellent solution to clean these injectors and intake ports. Additionally, some owners report issues with the active suspension system or air spring leaks, which are sensitive to fluid contamination, highlighting the importance of using pure, uncontaminated synthetic fluids throughout the vehicle. Finally, the 8-speed automatic transmission can sometimes exhibit harsh shifting or shuddering, particularly after high mileage, which can be smoothed out and protected against wear by switching to a high-performance synthetic transmission fluid like the AMSOIL Signature Series.