2018 Kenworth T680 Fluid Type Specifications

Quick reference

Fluid	Type/Spec	Capacity (approximate)
Engine Oil	Volvo VDS-4.5 / API CK-4 (or newer) SAE 10W-30 or 15W-40	40-48 quarts (varies)
Engine Coolant	Cummins CES 14603 / Volvo VCS-3 (OAT, red/purple)	60-75 quarts (varies)
Transmission Fluid	Eaton PS-386 (for Endurant/Fuller Advantage AMT) / Allison TES-295 (for automatic) / API GL-4 or GL-5 (for manuals)	Varies significantly
Front Differential	API GL-5, SAE 80W-90, 85W-140 (check axle spec)	Varies significantly
Rear Differential	API GL-5, SAE 80W-90, 85W-140 (check axle spec)	Varies significantly
Brake Fluid	DOT 4 (for hydraulic brakes, if equipped)	As needed
Power Steering	Eaton PS-164 Rev 7 / Dexron III	Varies with system
Washer Fluid	Commercial Washer Fluid (freeze-protected)	1-2 gallons
DEF	ISO 22241 / API DEF certified	10-20 gallons

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Engine Oil

For the 2018 Kenworth T680, engine oil specifications will primarily depend on the engine installed. Most commonly, you'd find Cummins or PACCAR engines. These engines typically require oils meeting stringent heavy-duty diesel engine specifications. The primary specification to look for is Volvo VDS-4.5 or API CK-4 (or newer, such as API FA-4, if specified for improved fuel economy and compatible with your particular engine). API CK-4 oils offer enhanced protection against oxidation, shear stability, and aeration, crucial for modern diesel engines with exhaust aftertreatment systems.

Viscosity

The most common viscosity grades for the 2018 T680 are SAE 10W-30 and SAE 15W-40. The appropriate viscosity will depend on ambient operating temperatures and manufacturer recommendations. Always consult your owner's manual for the specific engine in your T680 (e.g., Cummins X15, PACCAR MX-13) to determine the exact viscosity and specification required.

Capacity

Engine oil capacity can vary significantly based on the engine model and oil pan size, typically ranging from 40 to 48 quarts (10 to 12 gallons). Always verify the exact capacity and fill level using the dipstick according to the manufacturer's procedure.

Intervals and Pitfalls

Oil change intervals for heavy-duty trucks can range from 20,000 miles to 80,000 miles or more, depending on factors like engine type, duty cycle, oil analysis results, and oil life monitoring systems. Adhering to the manufacturer's recommended severe service intervals for arduous operating conditions is crucial. Using oil that does not meet the specified VDS-4.5 or API CK-4 standards can lead to premature wear of engine components, reduced diesel particulate filter (DPF) life, and potential warranty voidance. Never mix different engine oil types or use automotive gasoline engine oils (e.g., API SP) in a heavy-duty diesel engine.

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Engine Coolant

The 2018 Kenworth T680 will typically use an Extended Life Coolant (ELC) which is an Organic Acid Technology (OAT) formulation. Common specifications to look for include Cummins CES 14603 for Cummins engines or Volvo VCS-3 for PACCAR engines. These coolants are usually red or purple in color, though color should never be the sole indicator of coolant type. They provide excellent corrosion protection for aluminum and other engine components and have a service life significantly longer than conventional coolants.

Capacity

Coolant capacity can vary widely based on the specific engine and cooling system configuration, typically ranging from 60 to 75 quarts (15 to 18.75 gallons) for the entire system.

Intervals and Pitfalls

ELCs generally have a service life of 600,000 miles, 12,000 hours, or 6 years, whichever comes first, but always refer to your specific engine manufacturer's recommendations. The most critical pitfall is mixing different types of coolants, especially OAT with conventional or Hybrid OAT (HOAT) coolants. Mixing can lead to a chemical reaction that depletes corrosion inhibitors, causes gel formation, and results in premature cooling system component failure. Always use deionized or distilled water for any coolant dilution if you are using concentrate, although pre-mixed 50/50 solutions are highly recommended for convenience and proper concentration.

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Transmission Fluid

Transmission fluid specifications for the 2018 Kenworth T680 will depend entirely on the transmission installed. Kenworth offers a variety of transmission options, including Eaton manual transmissions, Eaton automated manual transmissions (AMT), and Allison automatic transmissions.

• Eaton Endurant / Fuller Advantage AMT: These modern automated manual transmissions often specify a proprietary fluid such as Eaton PS-386. This fluid is designed for extended drain intervals and optimal performance in these sophisticated units.
• Allison Automatic Transmissions: If your T680 is equipped with an Allison automatic transmission (e.g., 3000 or 4000 series), it will require a fluid meeting the Allison TES-295 specification. This is a synthetic fluid designed for very long drain intervals and optimized for Allison's electronic controls.
• Manual Transmissions (Older/Other applications): For manual transmissions, the requirement might be an API GL-4 or GL-5 rated gear oil, with viscosity such as SAE 50, 75W-90, or 80W-90, depending on the specific model. Always verify with your owner's manual or the transmission's data tag.

Capacity

Transmission fluid capacity varies significantly by model, from approximately 16-20 quarts for an Allison automatic to perhaps 20-30 pints for an Eaton manual/AMT.

Intervals and Pitfalls

Follow manufacturer guidelines strictly. Using the wrong fluid type or a "universal" ATF/gear oil can lead to premature wear, poor shifting performance, and catastrophic transmission failure. For Eaton AMTs and Allison automatics, using the specified synthetic fluid is paramount for achieving the designed long drain intervals and maintaining warranty.

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Differential Fluid (Front and Rear)

Kenworth T680s typically use heavy-duty hypoid gear oil for both front (if applicable) and rear differentials. The primary specification is API GL-5, which indicates an oil suitable for hypoid gears operating under high-speed/shock load, high-speed/low torque, and low-speed/high torque conditions.

Viscosity

Common viscosity grades include SAE 80W-90 for general use and SAE 85W-140 for severe service, high temperatures, or heavier loads. The specific axle manufacturer (e.g., Meritor, Dana) and axle model will dictate the precise requirement.

Capacity

Differential fluid capacity varies widely by axle model and ratio, typically ranging from 15 to 50 pints (7.5 to 25 quarts) per axle.

Intervals and Pitfalls

Differential fluid change intervals can range from 100,000 miles to 500,000 miles or more, often extended with synthetic fluids and regular oil analysis. Using anything less than API GL-5 can result in rapid gear wear. Some heavy-duty differentials may benefit from a synthetic API GL-5 fluid for extended life and improved fuel economy. Always ensure the correct viscosity is used for the operating environment and load conditions. If your truck has a limited-slip differential (uncommon in most heavy-duty applications but possible), it would require an LSD additive or a fluid specifically formulated for limited-slip applications.

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Brake Fluid

Most 2018 Kenworth T680 trucks are equipped with air brakes, which do not use hydraulic fluid like passenger cars. However, if your specific T680 configuration includes hydraulic brakes (e.g., for certain medium-duty applications or specific options), it will typically require DOT 4 brake fluid. DOT 4 has a higher wet and dry boiling point than DOT 3, offering better performance under heavy braking conditions.

Intervals and Pitfalls

Brake fluid (if hydraulic) should be changed every 2-3 years, as it is hygroscopic and absorbs moisture over time, which lowers its boiling point and can lead to corrosion in the brake system. Never mix DOT 4 with DOT 5 (silicone-based) fluid, as this can cause severe damage to the brake system components.

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Power Steering Fluid

For the 2018 Kenworth T680, power steering fluid specifications can vary. Many heavy-duty power steering systems specify a specialized fluid, often meeting Eaton PS-164 Rev 7. Some systems may also use an automatic transmission fluid (ATF) such as Dexron III (or a compatible multi-vehicle ATF that meets such specifications). Always check your owner's manual or the power steering pump reservoir cap for the exact specification.

Capacity

Power steering fluid capacity varies with the system, typically a few quarts.

Intervals and Pitfalls

While often overlooked, power steering fluid should be inspected regularly and changed periodically, typically every 100,000 to 150,000 miles or every few years, especially if it appears dark or smells burnt. Using the wrong type of fluid can lead to pump noise, reduced steering assistance, and premature component wear.

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Washer Fluid

The 2018 Kenworth T680 uses standard commercial windshield washer fluid. It is crucial to use a high-quality freeze-protected commercial washer fluid, especially if operating in cold climates. These fluids contain detergents for effective cleaning and alcohol to prevent freezing.

Capacity

Washer fluid reservoir capacity is typically 1-2 gallons.

Intervals and Pitfalls

Refill as needed. In colder climates, never use plain water, as it will freeze and can damage the reservoir, pump, and lines.

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Diesel Exhaust Fluid (DEF)

For all 2018 Kenworth T680 trucks equipped with selective catalytic reduction (SCR) systems (which is standard for achieving modern emissions standards), Diesel Exhaust Fluid (DEF) is required. DEF must meet the ISO 22241 standard and be API DEF certified. This ensures the fluid is pure 32.5% urea solution necessary for the proper function and longevity of the SCR system.

Capacity

DEF tank capacities on a Kenworth T680 typically range from 10 to 20 gallons.

Intervals and Pitfalls

DEF is consumed at a rate of approximately 2-3% of fuel consumption, meaning for every 100 gallons of diesel, you'll use 2-3 gallons of DEF. You will need to refill the DEF tank regularly. The most critical pitfall is using contaminated or non-spec DEF, which can lead to costly damage to the SCR system, significantly reduce its efficiency, and potentially derate the engine or prevent it from starting. Always store DEF in a cool, dry place away from direct sunlight, and ensure dispensing equipment is clean and dedicated to DEF use only. Never put DEF in the diesel tank or vice-versa.

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