Maintaining the fluid health of your 2018 Kia SOUL equipped with the 1.6L four-cylinder engine is essential for ensuring longevity, fuel efficiency, and consistent performance. This vehicle is designed to operate with specific lubricants that can withstand varying driving conditions, from daily city commutes to highway cruising. Using the correct viscosity and formulation helps prevent premature wear, reduces friction, and keeps internal components clean. Proper lubrication also safeguards critical systems like the transmission, cooling loop, and braking mechanism, ensuring they function reliably year after year.
Recommended AMSOIL Products
- AMSOIL Signature Series 5W-20 100% Synthetic Motor Oil – The top-tier choice offering up to 25,000 miles of protection, exceptional horsepower retention, and superior wear resistance for the 1.6L engine.
- AMSOIL Extended-Life 5W-20 100% Synthetic Motor Oil – Delivers up to 20,000 miles of protection with enhanced cleaning power to keep the engine running smoothly and reduce carbon buildup.
- AMSOIL OE 5W-20 100% Synthetic Motor Oil – A cost-effective synthetic option that fights sludge and deposits, meeting standard service intervals while providing robust engine protection.
- AMSOIL 5W-20 100% Synthetic High-Mileage Motor Oil – Formulated specifically for vehicles with over 75,000 miles, featuring additives that reduce sludge, minimize leaks, and restore engine performance.
- AMSOIL Oil Filter – An exceptional filter that captures 99% of harmful contaminants at 20 microns, designed to match the extended life capabilities of AMSOIL synthetic oils.
- WIX Oil Filter – A premium aftermarket filter option that offers superior media and performance compared to standard OEM filters, compatible with the OE and High-Mileage oil options.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A ready-to-use 50/50 ethylene glycol pre-mix that protects the cooling system for up to 150,000 miles or 5 years, compatible with all coolant colors.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated, non-toxic solution that requires mixing and offers extended service intervals up to 150,000 miles or 5 years with superior corrosion protection.
- AMSOIL Signature Series Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – Designed to withstand heavy towing and high temperatures while maintaining fluidity in sub-zero conditions for extended drain intervals.
- AMSOIL OE Fuel-Efficient 100% Synthetic Automatic Transmission Fluid – An OE-specification fluid that protects against wear and provides reliable performance for standard driving schedules.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Ensures excellent ABS and traction-control responsiveness with a stable viscosity across a wide temperature range for safer stopping power.
Engine Oil Specifications and Selection
The heart of your 2018 Kia SOUL is the 1.6-liter four-cylinder engine, identified by engine code [2] 2. This powerplant requires a specific viscosity to ensure proper lubrication during cold starts and under high operating temperatures. The manufacturer recommends SAE 5W-20 for all temperatures, noting that while 5W-30 or 10W-30 (above -18°C) are technically listed in some charts, 5W-20 is the preferred grade for optimal fuel economy and protection.
The total oil capacity, including a filter replacement, is 3.8 quarts. It is crucial to refill the engine with the correct amount and torque the drain plug to between 25 and 32 ft/lbs. Always check the oil level after refilling to ensure it is at the appropriate mark on the dipstick.
Transmission and Fluid Capacities
Keeping the transmission system healthy is just as vital as protecting the engine. For the automatic transmission (A6GF1), the total fill capacity is 7.1 quarts. This fluid is subject to high heat and stress, especially in stop-and-go traffic typical of urban driving. AMSOIL synthetic transmission fluids are engineered to remain fluid in sub-zero temperatures while resisting breakdown at elevated temperatures, providing a buffer against wear and sludge formation.
Cooling system maintenance cannot be overlooked. The 2018 SOUL with the automatic transmission requires 5.3 quarts of coolant, while the manual transmission variant (MTXL) calls for 5.4 quarts. AMSOIL antifreeze and coolant products use a unique poly-organic acid technology that protects all cooling system metals, gaskets, and hoses. These formulations are phosphate-, nitrate-, nitrite-, silicate-, borate-, and amine-free, making them compatible with various vehicle models and coolant colors.
Brake Fluid and Safety Systems
The braking system on the Kia SOUL relies on DOT 3 or DOT 4 specifications to meet FMVSS116 standards. Over time, brake fluid absorbs moisture from the air, which can lead to a lower boiling point and reduced braking efficiency. AMSOIL’s synthetic DOT 3 and DOT 4 brake fluid offers a stable viscosity range and excellent responsiveness, ensuring your ABS and traction control systems function correctly even when pushed to their limits.
Protecting Your Investment with Quality Additives
In addition to changing the primary lubricants, using performance additives can further enhance the vehicle’s operation. AMSOIL P.i. Performance Improver is designed to restore up to 14% horsepower and clean fuel injectors, particularly beneficial for vehicles with gasoline direct injection (GDI) engines. This additive helps control pre-ignition knock and reduces the need for higher-octane fuels, improving overall fuel economy and engine smoothness.
For owners who store their vehicles or use them seasonally, AMSOIL Engine Fogging Oil is an excellent choice to protect internal components during periods of inactivity. It creates a protective coating on cylinders and pistons to prevent rust and corrosion. Similarly, gasoline stabilizers can keep gasoline fresh for up to 12 months, preventing varnish and gum buildup that can clog filters and injectors.
Maintenance Best Practices
While AMSOIL synthetic lubricants allow for extended service intervals, regular inspections are still necessary. Checking fluid levels, looking for leaks, and listening for unusual noises can catch issues before they become major problems. When performing an oil change, ensure you use a high-quality filter like the AMSOIL Oil Filter or the WIX Oil Filter to guarantee that contaminants are removed from the circulating oil. The greater capacity of these filters compared to standard OEM units helps trap more wear-causing particles, extending the life of the engine.
About the Vehicle
The 2018 Kia SOUL represents a unique position in the automotive market, blending the practicality of a subcompact crossover with a distinctive boxy design that stands out on the road. Originally introduced as a quirky alternative to traditional hatchbacks, the second-generation SOUL, which includes the 2018 model year, refined this concept into a more refined yet still characterful vehicle. The “boxy” aesthetic was not just for show; it provided a surprisingly spacious interior, offering generous headroom and legroom that belies the car’s compact footprint. This interior volume is a hallmark of the SOUL, making it a favorite for drivers who value utility and comfort over aerodynamic sleekness.
Under the hood, the 1.6L four-cylinder engine provides a balance of fuel efficiency and adequate power for daily commuting and city driving. While not a high-performance sports car, the SOUL delivers a smooth and predictable driving experience that appeals to a wide demographic, from young first-time buyers to families needing a reliable secondary vehicle. The vehicle’s origin in Korea reflects Kia’s broader strategy of offering high-value vehicles that compete directly with established competitors in the United States and global markets. The SOUL is part of the brand’s push to diversify their lineup beyond sedans and SUVs, targeting a market segment that values customization and individuality.
Owners of the 2018 Kia SOUL often cite the vehicle’s unique styling, spacious cargo area, and user-friendly technology as key reasons for their purchase. The design language, characterized by its “urban cube” shape, allows for a customizable ownership experience where owners can modify the appearance with various decals and accessories. This sense of personalization contributes to a loyal following, as drivers treat their SOULs as a canvas for self-expression.
Despite its reliability, like any vehicle, the 2018 Kia SOUL has specific areas where maintenance can prevent common issues. One known concern for this model is the potential for oil consumption or sludge buildup if synthetic oil is not used or if changes are delayed. Conventional oils can break down faster under the heat generated by the engine, leading to carbon deposits on the pistons. AMSOIL Signature Series 5W-20 100% Synthetic Motor Oil addresses this by providing superior thermal stability and a robust detergent package that keeps the engine clean, preventing the sludge that can choke oil passages and starve components of lubrication.
Another common issue for the SOUL involves the automatic transmission fluid degrading over time, leading to rough shifting or delayed engagement. The fluid can become contaminated with metal shavings and varnish, which affects the transmission’s ability to operate smoothly. Switching to a high-performance synthetic transmission fluid like AMSOIL’s Fuel-Efficient Automatic Transmission Fluid can mitigate this by resisting oxidation and maintaining viscosity, ensuring smooth gear changes throughout the fluid’s life.
Cooling system reliability is also a critical point for this vehicle. Over time, the coolant can become acidic or lose its anti-corrosive properties, leading to corrosion in the radiator or water pump. This can cause overheating, which is particularly detrimental to the engine’s longevity. Using a premium AMSOIL Propylene Glycol Antifreeze provides a stronger defense against corrosion and cavitation, protecting the metal components inside the cooling system for longer periods.
Finally, brake fluid contamination is a universal issue that can affect the 2018 SOUL. As the fluid absorbs moisture, its boiling point drops, which can lead to a spongy pedal feel or brake fade during heavy use. AMSOIL DOT 3 and DOT 4 synthetic brake fluid resists moisture absorption better than conventional fluids, maintaining a high boiling point and ensuring consistent pedal feel and safety, thereby addressing a common wear point in the braking system.