2019 Peterbilt 579 Fluid and Lubricant Specifications

As an ASE-certified master technician, I know that using the correct fluids and lubricants is the single most important thing you can do to ensure the longevity and reliability of your 2019 Peterbilt 579. These heavy-duty trucks are built to last, but they require specific formulations to protect their advanced components. Using the wrong fluid can lead to premature wear, costly breakdowns, and even void your warranty.

This guide covers all the essential factory-spec fluids for your 2019 Peterbilt 579, whether it's equipped with a PACCAR MX or Cummins X15 engine. Always double-check your owner's manual or OEM service information for the most precise specifications for your truck's particular configuration.

Quick Reference

Fluid	Type/Spec	Capacity
Engine Oil	API CK-4; SAE 15W-40 or 10W-30	44 quarts / 11 gal (PACCAR MX-13) or 12 gal (Cummins X15)
Engine Coolant	Peterbilt ELC (OAT); Nitrite-Free	~12 - 14 gallons (Varies with configuration)
Transmission Fluid	Varies by transmission model	Varies widely
Rear Axle / Differential	Dana SHAES 256 REV C; SAE 75W-90	~34 - 38 pints (Varies by axle)
Brake Fluid	DOT 3 or DOT 4 Hydraulic Fluid	N/A
Power Steering Fluid	Power Steering Fluid	~2 - 4 quarts
Windshield Washer Fluid	Winter/Summer blend as needed	~1 gallon
Diesel Exhaust Fluid (DEF)	ISO 22241	~10 - 20 gallons

Engine Oil

The engine is the heart of your Peterbilt 579, and using the correct specification oil is critical for protecting it under extreme loads. For 2019 models, the required specification is API Service CK-4.

• Viscosity: The most commonly recommended viscosity grades are SAE 15W-40 for all-around performance and SAE 10W-30 for improved fuel economy and cold-weather performance.
• Specification: The oil must meet the CK-4 performance standard. For PACCAR MX engines, look for oils meeting CES 20086. For Cummins X15 engines, look for CES 20086 approval.
• Capacity: A PACCAR MX-13 engine holds approximately 44 quarts (11 gallons), while a Cummins X15 holds approximately 12 gallons. Always verify the level with the dipstick after filling.
• Notes: Never use older specification oils (like CJ-4) unless specifically approved for your engine, as they may not provide adequate protection for modern emissions components.

Engine Coolant

Modern heavy-duty engines require specific coolant formulations to prevent corrosion of mixed metals. The 2019 Peterbilt 579 uses a Nitrite-Free Organic Acid Technology (OAT) Extended Life Coolant (ELC).

• Type: Peterbilt ELC (Red/Pink), which is a Nitrite-Free OAT formulation.
• Specification: Do not mix with conventional green or HD coolants containing nitrites. If topping off, use only a compatible Nitrite-Free OAT ELC.
• Capacity: The total system capacity typically ranges from 12 to 14 gallons, but varies based on the engine and chassis configuration.
• Notes: Mixing coolant types can cause gelling and blockages in the radiator and heater core, leading to severe engine overheating. If the coolant type is unknown, a complete flush and fill with the specified OAT ELC is the safest course of action.

Transmission Fluid

The correct fluid for your transmission depends entirely on which model is installed in your truck—an automated Eaton Endurant, an Allison automatic, or a manual transmission.

• Eaton Endurant / Automated Manuals: Use a fluid meeting PS-386 (formerly PS-164 rev 7) specification.
• Allison Automatics: Use a TES 295 approved fluid, such as TranSynd.
• Manual Transmissions (Eaton, etc.): Typically use a PS-386 heavy-duty synthetic gear lubricant.
• Notes: This is one of the most critical fluids to get right. "Universal" transmission fluids are not recommended. Always verify the required fluid by checking the data plate on the side of the transmission itself.

Rear Axle / Differential

The rear axles require a robust gear oil to handle the immense torque and pressure.

• Type: Fully synthetic SAE 75W-90 gear lubricant.
• Specification: For Dana axles, the required specification is SHAES 256 REV C.
• Capacity: Tandem axles can hold between 34 and 38 pints total, depending on the specific model. Always fill to the bottom of the fill plug hole.
• Notes: Ensure you are using a high-quality synthetic oil meeting the correct Dana specification. Using a lower-quality GL-5 mineral oil can reduce the axle's life and service interval.

Brake Fluid

The 2019 Peterbilt 579 uses an air brake system for its primary stopping power. However, it may have a hydraulic clutch system that uses brake fluid.

• Type: DOT 3 or DOT 4 Brake Fluid.
• Notes: This applies only to the clutch master cylinder reservoir, not the air brake system. The air system uses an air dryer to remove moisture, and the cartridge should be serviced regularly.

Power Steering Fluid

• Type: Conventional Power Steering Fluid.
• Capacity: The system typically holds between 2 and 4 quarts.
• Notes: While some systems can tolerate automatic transmission fluid, it is best practice to use a fluid specifically labeled for power steering systems to ensure seal compatibility and proper lubrication.

Windshield Washer Fluid

• Type: Use a commercial windshield washer solvent. Use a freeze-resistant "winter" blend in colder climates to prevent the reservoir and lines from freezing and cracking.
• Capacity: Typically around 1 gallon.

Diesel Exhaust Fluid (DEF)

DEF is essential for the operation of the Selective Catalytic Reduction (SCR) system in your 2019 Peterbilt 579.

• Type: Diesel Exhaust Fluid certified by the American Petroleum Institute (API).
• Specification: Must meet ISO 22241.
• Notes: Never add anything other than DEF to the DEF tank. Contamination with fuel, water, or coolant will destroy the expensive SCR system components. Always use fresh, properly stored DEF from a reputable source.

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