2016 Peterbilt 579 Fluid Type Specs

Quick reference

Fluid	Type/Spec	Capacity (approximate)
Engine Oil	SAE 10W-30 or 15W-40, API CK-4 / FA-4 (engine dependent)	36-44 Quarts
Engine Coolant	ELC (Extended Life Coolant), OAT, Red/Purple, CAT EC-1	60-80 Quarts
Transmission	Eaton PS-386 (manual), Allison TES-295 / TES-389 (auto)	13-19 Quarts (auto)
Front Diff.	Meritor O-76N, SAE 75W-90 / 80W-90	18-22 Pints
Rear Diff.	Meritor O-76N, SAE 75W-90 / 80W-90	18-22 Pints (each)
Brake Fluid	N/A (Air Brakes)	N/A
Power Steering	Eaton PS-164 Rev 7, Chevron 1000 THF, Dexron III	10-16 Quarts
Washer Fluid	Commercial Washer Fluid	1-3 Gallons
DEF	ISO 22241 (API Certified)	10-20 Gallons

Engine Oil

For the 2016 Peterbilt 579, the engine oil specification is highly dependent on the specific engine installed. Peterbilt offers various engine options, including PACCAR MX-13, Cummins ISX15, and sometimes others. Generally, these heavy-duty diesel engines require oils meeting API CK-4 or API FA-4 standards.

• API CK-4 oils are backward compatible and often recommended for older engines or those operating under severe conditions. Common viscosities include SAE 15W-40.
• API FA-4 oils are designed for newer engines to provide improved fuel economy. They are typically lower viscosity, such as SAE 10W-30, and are not backward compatible with engines that do not specifically call for FA-4.

Always consult your owner's manual or the engine manufacturer's specifications to determine the correct API classification and viscosity for your specific engine. The capacity will vary between 36 to 44 quarts depending on the engine model.

Intervals: Typical oil change intervals for heavy-duty trucks can range from 15,000 to 50,000 miles or more, depending on load, operating conditions, and oil analysis results. Using an oil analysis program is highly recommended to optimize drain intervals.

Pitfalls: Never mix API CK-4 and FA-4 oils unless explicitly stated by your engine manufacturer. Using FA-4 oil in an engine not designed for it can lead to premature wear. Always ensure the oil meets the specific OEM requirements for your engine (e.g., PACCAR's own specifications for MX engines).

Engine Coolant

The 2016 Peterbilt 579 typically utilizes an Extended Life Coolant (ELC), which is an Organic Acid Technology (OAT) formula. These coolants are usually red or purple in color. A common specification for these coolants is CAT EC-1, though Peterbilt also has its own recommended coolants that meet or exceed this specification.

Capacity: The cooling system capacity can range from 60 to 80 quarts, depending on the engine and chassis configuration.

Intervals: ELC coolants offer extended service life, often up to 600,000 miles, 12,000 hours, or 6 years, with proper maintenance and SCA (Supplemental Coolant Additive) testing/replenishment if not a "fill for life" product. Always verify the specific interval in your owner's manual.

Pitfalls: Mixing different coolant technologies (e.g., OAT with traditional silicated coolants) can lead to gel formation, corrosion, and severe cooling system damage. Only use distilled water if mixing concentrate. Never use only water. Ensure proper coolant concentration is maintained for adequate freeze protection and corrosion inhibition.

Transmission Fluid

The transmission fluid type for your 2016 Peterbilt 579 will depend entirely on the transmission installed.

• Manual Transmissions (e.g., Eaton Fuller): Many Eaton manual transmissions specify their own proprietary fluid, such as Eaton PS-386. Some may allow for approved heavy-duty engine oils (e.g., SAE 50 synthetic) or specialized gear oils. Always refer to the Eaton owner's manual for the precise specification.
• Automatic Transmissions (e.g., Allison): Allison automatic transmissions, common in the 579, require fluids meeting their specific TES (Transmission Engineering Specification) standards. For the 2016 model year, you'll typically find Allison TES-295 or the newer TES-389 (Dexron III H/G equivalent). TES-295 is a premium synthetic fluid offering extended drain intervals. Capacities for automatic transmissions are typically 13-19 quarts.

Intervals: Manual transmission intervals can range from 250,000 to 500,000 miles. Allison TES-295 fluids offer extended drains, often up to 150,000 miles, but this can vary based on duty cycle and filter changes. Always refer to the manufacturer's guide.

Pitfalls: Never use unapproved fluids in any transmission. Using the wrong fluid can lead to premature wear, shifting problems, and transmission failure. Allison and Eaton transmissions are particularly sensitive to fluid type. "Universal" fluids should be avoided.

Differential Fluid (Front and Rear)

The 2016 Peterbilt 579 typically uses Meritor axles. For these axles, the recommended differential fluid often adheres to Meritor O-76N specifications. This usually translates to a heavy-duty synthetic gear oil.

• Type: SAE 75W-90 or SAE 80W-90 synthetic gear oil is commonly specified. Some applications, especially those under heavy load, might recommend SAE 80W-140. Limited-slip differentials (LSD), if equipped, would require an LSD additive or a gear oil already containing friction modifiers, but LSDs are uncommon in heavy-duty truck differentials.

Capacity: Each differential typically holds between 18-22 pints (9-11 quarts).

Intervals: Differential fluid change intervals can be very long for synthetic oils, often 250,000 to 500,000 miles or more, depending on the manufacturer's recommendations and operating conditions.

Pitfalls: Using conventional gear oil where synthetic is specified can reduce efficiency and component life. Ensure the fluid meets the Meritor O-76N standard for optimal performance and warranty compliance.

Brake Fluid

The 2016 Peterbilt 579 uses an air brake system, not a hydraulic brake fluid system. Therefore, there is no traditional brake fluid (DOT 3, 4, 5.1) to service. The system relies on compressed air to operate the brakes.

Pitfalls: While there's no fluid, proper maintenance of the air dryer and regular draining of air tanks are crucial to prevent moisture buildup and system corrosion, which can lead to brake issues.

Power Steering Fluid

For the 2016 Peterbilt 579, the power steering system commonly specifies a heavy-duty hydraulic fluid.

• Type: Common specifications include Eaton PS-164 Rev 7. Many manufacturers will also recommend Chevron 1000 THF (Tractor Hydraulic Fluid) or fluids that meet Dexron III specifications, particularly for systems with combined power steering and hydraulic functions. Always verify the specific fluid type in your owner's manual or service information.

Capacity: The power steering reservoir capacity is typically 10-16 quarts.

Intervals: Power steering fluid is often considered "lifetime" fill by some, but it's good practice to inspect its condition regularly and consider replacement every 100,000 to 200,000 miles or if contamination is observed.

Pitfalls: Using an incompatible fluid can lead to pump failure, seal degradation, and noisy operation. Ensure the fluid meets the specific requirements of the power steering pump and steering gear.

Washer Fluid

This system is straightforward.

• Type: Any good quality year-round commercial washer fluid designed for automotive use is suitable. Many formulations offer freeze protection and bug/grime removal properties.

Capacity: The washer fluid reservoir typically holds 1 to 3 gallons.

Intervals: Top off as needed.

Pitfalls: Do not use plain water, especially in cold climates, as it can freeze and damage the reservoir and pump. Avoid household cleaners that are not formulated for automotive use, as they can damage paint or trim.

Diesel Exhaust Fluid (DEF)

For the emissions system on diesel-powered 2016 Peterbilt 579s, Diesel Exhaust Fluid (DEF) is mandatory for Selective Catalytic Reduction (SCR) systems.

• Type: DEF must meet ISO 22241 standards and be API Certified. It is a high-purity urea solution (32.5% urea in de-ionized water). Inferior DEF can damage the SCR system.

Capacity: DEF tank capacities typically range from 10 to 20 gallons.

Intervals: DEF is consumed continually while the engine is running. Refill as needed. Modern trucks have DEF level gauges and warnings.

Pitfalls: Never put DEF in the diesel fuel tank, and never put diesel fuel in the DEF tank; this will cause severe and immediate damage to respective systems. Store DEF properly to avoid contamination and extreme temperatures (freezing and excessive heat can degrade its effectiveness). Use only API-certified ISO 22241 DEF.

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