2020 GMC Sierra 2500HD Fluid Specifications

As an ASE-certified master technician, I've compiled this comprehensive fluid specification sheet for your 2020 GMC Sierra 2500HD. Adhering to manufacturer specifications is crucial for the longevity and performance of your truck. Using the incorrect fluid type or specification can lead to premature wear, reduced efficiency, and costly repairs.

Quick reference

Fluid	Type/Spec	Capacity
Engine Oil (Gasoline)	SAE 0W-20, API SN Plus or later, dexos1 Gen2 (or Gen3)	8 quarts (7.6 liters) with filter
Engine Oil (Diesel)	SAE 5W-40 or 15W-40, API CK-4, dexosD	10 quarts (9.5 liters) with filter
Engine Coolant	Dex-Cool (Orange), OAT, GM6277M	~16-18 quarts (15.1-17 liters) - verify in owner's manual for exact
Transmission Fluid	Dexron HP (10L1000 Automatic Transmission)	~13.5 quarts (12.8 liters) for drain and fill; ~17.5 quarts (16.6 liters) for overhaul
Transfer Case	AutoTrak II (Blue), GM Part No. 88900199 or equivalent	~1.5 - 2 quarts (1.4 - 1.9 liters) - verify in owner's manual
Front Differential	SAE 75W-90 Synthetic Axle Lubricant, GM Part No. 88901291	~1.8 - 2.1 quarts (1.7 - 2 liters) - verify in owner's manual
Rear Differential	SAE 75W-90 Synthetic Axle Lubricant, GM Part No. 88901291	~2.5 - 3 quarts (2.4 - 2.8 liters) - verify in owner's manual
Brake Fluid	DOT 3 or DOT 4	As needed
Power Steering Fluid	Dexron VI Automatic Transmission Fluid	As needed
Washer Fluid	GM Optikleen concentrate or good quality washer fluid	~1 gallon (3.8 liters)
Diesel Exhaust Fluid	Per ISO 22241	~7-gallon (26.5 liters) tank

Engine Oil

Your 2020 GMC Sierra 2500HD comes with two primary engine options: the 6.6L V8 gasoline engine and the 6.6L Duramax turbo-diesel engine each requiring specific engine oil types.

6.6L V8 Gasoline Engine

Type/Spec: SAE 0W-20, meeting API SN Plus or a later specification (API SP recommended) and GMs dexos1 Gen2 specification. For optimal performance and protection, especially in newer models, using oil that meets the dexos1 Gen3 specification is highly recommended as it offers improved protection against low-speed pre-ignition (LSPI).

Capacity: Approximately 8 quarts (7.6 liters) with a filter change.

Intervals: The Oil Life Monitoring (OLM) system should be followed. Under normal driving conditions, this can range from 7,500 to 10,000 miles or 12 months, whichever comes first. However, severe duty cycles (towing, extreme temperatures, dusty conditions) will shorten this interval.

Pitfalls: Never use an oil that does not meet the dexos1 specification. Using conventional oil or an oil with an incorrect viscosity can lead to increased engine wear and potentially void your powertrain warranty.

6.6L Duramax Turbo-Diesel Engine

Type/Spec: SAE 5W-40 or 15W-40, meeting API CK-4 specification and GMs dexosD specification. The choice between 5W-40 and 15W-40 often depends on ambient temperatures. Refer to your owner's manual for the recommended viscosity based on your climate.

Capacity: Approximately 10 quarts (9.5 liters) with a filter change.

Intervals: Similar to the gasoline engine, follow the Oil Life Monitoring (OLM) system. Diesel engines often have more stringent requirements due to soot loading and higher operating temperatures, so closer attention to the OLM and potentially shorter intervals for heavy use are advised.

Pitfalls: Using conventional engine oil or a specification older than API CK-4 (e.g., CJ-4) can lead to premature wear of engine components, particularly those related to the exhaust aftertreatment system. Always ensure the oil carries the dexosD approval for your Duramax engine.

Engine Coolant

Type/Spec: Your 2020 GMC Sierra 2500HD uses Dex-Cool extended-life engine coolant, which is an Organic Acid Technology (OAT) coolant. It is typically orange in color and meets GM specification GM6277M.

Capacity: Approximately 16-18 quarts (15.1-17 liters) for the system when completely drained and refilled. Always verify the exact capacity in your owner's manual or OEM service information.

Intervals: Factory-filled Dex-Cool is designed for a long service life, often up to 5 years or 150,000 miles, whichever comes first. However, regular inspection of coolant levels and condition is crucial.

Pitfalls: Never mix Dex-Cool with traditional green, yellow, or hybrid OAT (HOAT) coolants. Mixing different coolant technologies can lead to chemical reactions, gelling, reduced corrosion protection, and severe damage to cooling system components. Always dilute concentrated coolant with distilled water to the manufacturer's recommended ratio (typically 50/50). If you are unsure of the coolant type, a complete flush and refill with the correct Dex-Cool is the safest approach.

Transmission Fluid

The 2020 GMC Sierra 2500HD is equipped with the 10-speed 10L1000 automatic transmission.

Type/Spec: This transmission requires Dexron HP (High Performance) Automatic Transmission Fluid. It is a specialized fluid for this particular transmission and is not interchangeable with other Dexron specifications like Dexron VI.

Capacity: A drain and fill typically requires around 13.5 quarts (12.8 liters). A complete overhaul or dry fill can be closer to 17.5 quarts (16.6 liters). Capacities can vary slightly, so always refer to the specific procedure in the OEM service manual.

Intervals: Transmission fluid change intervals can vary significantly based on driving conditions. For severe duty (towing, heavy hauling, frequent stop-and-go), earlier changes are recommended, often around 45,000 miles. Under normal conditions, intervals can be extended, but regular checks of fluid level and condition are key.

Pitfalls: Never use universal ATF or any fluid other than Dexron HP. These transmissions are highly sensitive to fluid properties. Using the incorrect fluid can lead to harsh shifts, transmission damage, and premature failure. Always verify the fluid type for your specific 10L1000 transmission.

Transfer Case Fluid (if 4WD/AWD)

Type/Spec: For 4x4 models, the transfer case requires AutoTrak II Fluid. This is a blue-colored fluid specifically designed for GM's AutoTrak transfer cases. The GM Part No. is 88900199 or an equivalent meeting the specification.

Capacity: Approximately 1.5 to 2 quarts (1.4 to 1.9 liters). Always verify the specific capacity in your owner's manual or OEM service information.

Intervals: Typically, every 50,000 miles or 5 years, but consult your owner's manual for specific recommendations based on driving conditions.

Pitfalls: Do not substitute with Dexron VI or any other automatic transmission fluid. AutoTrak II has specific friction modifiers and properties critical for the proper operation and longevity of the transfer case clutch pack.

Differential Fluid (Front and Rear)

Type/Spec: Both the front and rear differentials typically require SAE 75W-90 Synthetic Axle Lubricant. GM specifies their own part number, such as GM Part No. 88901291 or equivalent, which is a full synthetic GL-5 rated gear oil. Vehicles equipped with a limited-slip differential (LSD), while less common on heavy-duty trucks, would require an LSD additive or a fluid that already contains the friction modifier. Always verify if your truck has an LSD (G80 RPO code for Eaton locker) and the oil requirement.

Capacity:

• Front Differential: Approximately 1.8 to 2.1 quarts (1.7 to 2 liters).
• Rear Differential: Approximately 2.5 to 3 quarts (2.4 to 2.8 liters).

Exact capacities can vary based on axle size and configuration, so always check your owner's manual or an OEM service manual.

Intervals: Differential fluid should generally be replaced every 50,000 to 100,000 miles, with shorter intervals advisable for heavy towing, off-road use, or frequent severe duty.

Pitfalls: Using conventional gear oil instead of synthetic can lead to premature wear. Ensure the fluid meets at least a GL-5 rating. If your truck has an Eaton G80 automatic locking differential, a specific additive is usually not required as it operates mechanically, however, good quality GL-5 synthetic 75W-90 is still paramount.

Brake Fluid

Type/Spec: Your 2020 GMC Sierra 2500HD requires DOT 3 or DOT 4 brake fluid. DOT 4 offers a higher boiling point than DOT 3, which can be beneficial for heavy-duty applications like towing, but both are compatible (DOT 4 is backward compatible with DOT 3). Never use DOT 5 (silicone-based) fluid, as it is incompatible with the ABS system and seals.

Capacity: As needed for maintenance or system flush. The reservoir keeps pace with pad wear.

Intervals: Brake fluid is hygroscopic (absorbs moisture), which lowers its boiling point and can lead to corrosion in the brake system. It is generally recommended to flush and replace brake fluid every 2-3 years, or especially if it appears dark or contaminated.

Pitfalls: Never mix DOT 3, DOT 4, or DOT 5.1 with DOT 5. Always ensure the fluid container is sealed before use, as brake fluid begins absorbing moisture from the air immediately upon opening.

Power Steering Fluid

Type/Spec: The power steering system in your Sierra 2500HD typically uses Dexron VI Automatic Transmission Fluid. While technically an ATF, it is the specified fluid for many modern GM power steering systems.

Capacity: As needed to maintain the proper level in the reservoir.

Intervals: Power steering fluid does not have a strict replacement interval, but it's good practice to inspect its condition regularly. If it appears dark, burnt, or has a strong odor, it should be changed or flushed.

Pitfalls: Using generic power steering fluid or an incorrect Dexron type can lead to pump noise, reduced steering assistance, and premature component failure.

Washer Fluid

Type/Spec: Any good quality windshield washer fluid that offers freeze protection appropriate for your climate can be used. GM also offers its Optikleen concentrate which can be mixed with water.

Capacity: Approximately 1 gallon (3.8 liters) in the reservoir.

Intervals: As needed.

Pitfalls: In colder climates, do not use plain water, as it can freeze and damage the washer system components.

Diesel Exhaust Fluid (DEF)

Type/Spec: For your Duramax diesel engine, Diesel Exhaust Fluid (DEF) must meet the ISO 22241 standard. This ensures the purity and quality required for the Selective Catalytic Reduction (SCR) system. Look for the API Diesel Exhaust Fluid Certification Mark.

Capacity: The DEF tank typically holds around 7 gallons (26.5 liters).

Intervals: Consumption rates vary based on driving style, load, and engine operation. The truck's DEF gauge and warning system will alert you when it's time to refill. Do not ignore these warnings.

Pitfalls: Never use contaminated DEF, or any fluid resembling DEF but not meeting the ISO 22241 standard. Using non-compliant DEF can severely damage the SCR system and lead to costly repairs and potential derating of the engine's power. Always store DEF in a cool, dry place and be mindful of its shelf life.

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