2023 Kenworth T680: Complete Fluid Specifications

Quick Reference: 2023 Kenworth T680 Fluids

Fluid	Type/Spec	Capacity
Engine Oil	API CK-4 or FA-4; SAE 15W-40, 10W-30	44 - 48 quarts (PACCAR MX-13)
Engine Coolant	Nitrite-Free OAT ELC (PACCAR ELC)	14 - 16 gallons
Transmission Fluid	Eaton PS-386 (Automated) / SAE 50 (Manual)	Varies with model
Rear Axle / Differential	SAE 75W-90 Synthetic Gear Oil (API GL-5)	18 - 22 pints per axle
Power Steering	ATF DEXRON III / Mercon	~4-6 quarts
Hydraulic Clutch Fluid	DOT 3 or DOT 4 Brake Fluid	~1-2 quarts
Windshield Washer Fluid	Standard Blue Washer Fluid	~2 gallons
Diesel Exhaust Fluid (DEF)	ISO 22241	10 - 25 gallons

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Engine Oil

The 2023 Kenworth T680, typically equipped with the PACCAR MX-11 or MX-13 engine, demands a high-quality, heavy-duty diesel engine oil that meets stringent performance standards. The primary specification to look for is API Service Category CK-4. For some applications focused on fuel economy, API FA-4 may be specified, but these oils are not interchangeable or backward-compatible with CK-4. Always verify the requirement in the owner's manual.

• Specification: API CK-4 (or FA-4 where specified). Look for Cummins CES 20086 and PACCAR PC-11 approvals.
• Viscosity: The most common viscosity grade is SAE 15W-40, suitable for a wide range of operating temperatures. In colder climates or for improved fuel economy, SAE 10W-30 is also a primary choice.
• Capacity: For the PACCAR MX-13, the oil system capacity is approximately 48 quarts (12 gallons) including the filter.

Technician's Note: Using an oil other than CK-4 or the specifically required FA-4 can lead to inadequate protection for the valve train, bearings, and emissions components (like the Diesel Particulate Filter or DPF). Oil change intervals can be up to 75,000 miles depending on duty cycle, but this requires oil analysis and adherence to the manufacturer's extended drain program.

Engine Coolant

Modern heavy-duty engines require specific coolant formulations to prevent corrosion, cavitation, and deposits in the cooling system, which includes the engine block, radiator, and EGR cooler. The T680 uses a Nitrite-Free Organic Additive Technology (OAT) Extended Life Coolant (ELC).

• Specification: PACCAR ELC (Red/Pink), meeting ASTM D6210 standards. This is a Nitrite-Free OAT formula.
• Type/Color: Red or Pink ELC.
• Capacity: The total system capacity is typically between 14 to 16 gallons.

Common Pitfall: Never mix coolants of different types or colors. Mixing a conventional (green) or a Nitrited OAT (NOAT) with the factory-spec Nitrite-Free OAT will compromise the extended life properties, leading to corrosion and sludge formation. If the system is contaminated, a complete flush and fill is required.

Transmission Fluid

The correct transmission fluid is entirely dependent on the specific transmission installed in the T680. The most common are Eaton's automated and manual gearboxes.

• Eaton Endurant (Automated): Requires Eaton PS-386, a synthetic lubricant designed for long life and fuel efficiency.
• Eaton Fuller (Manual): These robust manual transmissions typically specify SAE 50 transmission lubricant conforming to Eaton's PS-164 revision 7 standard.

Technician's Note: Using a generic gear oil or ATF in place of the specified lubricants is a critical error. The PS-386 spec is essential for the proper operation of clutches and shift mechanisms in automated transmissions. Using the wrong fluid can cause irreparable damage. Always identify the transmission by its data tag before servicing.

Rear Axle / Differential Fluid

The drive axles on a T680 handle immense torque and require a robust, shear-stable gear lubricant. The standard for line-haul applications is a synthetic gear oil that promotes longevity and fuel efficiency.

• Specification: API GL-5, MIL-PRF-2105E. Look for lubricants approved to a specific axle manufacturer spec like Dana SHAES 256 Rev C or Meritor O-76.
• Viscosity: SAE 75W-90 Synthetic Gear Oil is the most common specification for tandem drive axles.
• Capacity: Each differential typically holds between 18 and 22 pints (9-11 quarts).

Technician's Note: Ensure the axle housing is clean before opening the fill plug to prevent contamination. When draining, inspect the magnetic drain plug for excessive metal debris, which could indicate an impending bearing or gear failure.

Power Steering Fluid

The power steering system in the T680 is a straightforward hydraulic system that typically uses a common and readily available fluid.

• Specification: Automatic Transmission Fluid (ATF) meeting DEXRON III / Mercon specifications is widely used and approved.

Technician's Note: While many fluids can work in a pinch, sticking to a quality DEXRON III/Mercon ATF ensures proper seal compatibility and hydraulic performance across all temperatures.

Hydraulic Clutch Fluid

For T680 models equipped with a manual transmission, the clutch is actuated hydraulically. This system uses standard automotive brake fluid.

• Specification: DOT 3 or DOT 4 Heavy-Duty Brake Fluid.

Common Pitfall: Do not use DOT 5 silicone-based fluid. It is not compatible with the seal materials in the clutch master and slave cylinders and will cause system failure. The fluid should be changed if it appears dark or contaminated, as moisture absorption can lead to a spongy clutch pedal.

Windshield Washer Fluid

Any standard, commercially available windshield washer solvent is acceptable.

• Specification: Standard blue windshield washer fluid.
• Technician's Note: In regions where temperatures fall below freezing, use a fluid with an appropriate antifreeze rating to prevent freezing in the reservoir, lines, and at the spray nozzles.

Diesel Exhaust Fluid (DEF)

DEF is critical for the operation of the Selective Catalytic Reduction (SCR) system, which reduces NOx emissions. DEF is a standardized fluid and must be handled correctly to prevent contamination.

• Specification: ISO 22241. This will be clearly marked on any reputable DEF container. It is a solution of 32.5% high-purity urea and 67.5% de-ionized water.
• Capacity: The onboard DEF tank typically holds between 10 and 25 gallons.

Common Pitfall: DEF is extremely sensitive to contamination. Using a dirty funnel or container, or allowing any other fluid (diesel fuel, oil, coolant) to enter the DEF tank will destroy the expensive SCR catalyst and aftertreatment system. Use only sealed containers and dedicated dispensing equipment.

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