2023 GMC Sierra 2500HD: Complete Fluid Specifications

Quick Reference

Fluid	Type/Spec	Capacity
Engine Oil (6.6L Gas V8)	0W-40 or 5W-40 dexosR	8.0 quarts
Engine Oil (6.6L Duramax Diesel)	15W-40 or 5W-40 API CK-4	10.0 quarts
Engine Coolant	DEX-COOL OAT	22.1 - 25.5 quarts
Transmission Fluid (10-spd Allison)	DEXRON ULV	~17.5 quarts (service fill)
Transfer Case Fluid	DEXRON VI	2.0 quarts
Front Differential Gear Oil	SAE 75W-90 Synthetic	1.8 quarts
Rear Differential Gear Oil	SAE 75W-90 Synthetic	3.6 quarts
Brake Fluid	DOT 3	As needed
Power Steering Fluid	N/A (Electric Assist)	N/A
Windshield Washer Fluid	-30°F All-Season	1.0 gallon
Diesel Exhaust Fluid (DEF)	ISO 22241	7.3 gallons

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Engine Oil

6.6L L8T Gas V8

• Type: SAE 0W-40 or 5W-40 Full Synthetic meeting dexosR specification.
• Capacity: 8.0 quarts (7.6 liters) with filter.

General Motors has transitioned its gasoline direct injection (GDI) engines to the latest dexosR specification for enhanced protection against Low-Speed Pre-Ignition (LSPI) and improved fuel economy. Using a non-licensed product is not recommended. For the 2023 model year, the recommended viscosity is a 0W-40 or 5W-40, a change from previous generation small blocks. Always confirm the oil cap or owner's manual for the correct grade. Change interval is dictated by the Oil Life Monitoring system, but should not exceed one year.

6.6L L5P Duramax Turbo-Diesel V8

• Type: SAE 15W-40 or 5W-40 (preferred in temps below 0°F) meeting API Service CK-4.
• Capacity: 10.0 quarts (9.5 liters) with filter.

The Duramax diesel demands a robust CK-4 rated oil to handle soot and protect turbocharger bearings. GM specifies the use of high-quality diesel engine oil. While 15W-40 is suitable for most climates, switching to a synthetic 5W-40 in winter months offers superior cold-start protection. As with the gasoline engine, follow the Oil Life Monitor for service intervals.

Engine Coolant

• Type: ACDelco DEX-COOL Orange, an Organic Acid Technology (OAT) extended-life coolant.
• Capacity: 22.1 to 25.5 quarts depending on configuration (e.g. single/dual radiator).

All 2023 Sierra HD trucks use GM's signature orange DEX-COOL coolant. This is an OAT-based formula designed for a service life of up to 5 years or 150,000 miles. It is critical not to mix this with other coolant types like older Inorganic Acid Technology (IAT "green") or Hybrid OAT (HOAT). Mixing can cause the coolant to gel, leading to blockages in the radiator, heater core, and engine passages. When topping off, use only DEX-COOL pre-mixed 50/50 with deionized water, or a concentrate mixed appropriately.

Transmission Fluid

• Type: ACDelco DEXRON ULV (Ultra-Low Viscosity) Automatic Transmission Fluid.
• Capacity: Approximately 17.5 quarts for a service fill; varies. Total system capacity is higher.

The Allison 10-speed automatic transmission (10L1000) is a sophisticated unit that requires a specific, ultra-low viscosity fluid. Do not use older DEXRON VI, MERCON LV, ATF+4, or any "universal" ATF. Using the wrong fluid will cause poor shifting, accelerated wear, and eventual transmission failure. Fluid change intervals are typically around 45,000 miles under severe use, but refer to your owner's manual for the specific schedule.

Transfer Case Fluid

• Type: ACDelco DEXRON VI Automatic Transmission Fluid.
• Capacity: 2.0 quarts (1.9 liters).

For 4WD models, the transfer case is lubricated by standard DEXRON VI ATF. It is a common mistake to assume it uses gear oil. Using a heavier fluid will lead to poor engagement of the 4WD system and potential damage. The fluid should be changed according to the severe service schedule, often around 45,000–50,000 miles.

Differential Gear Oil

• Front Differential (4WD models): SAE 75W-90 Synthetic Gear Oil. Capacity: ~1.8 quarts.
• Rear Differential: SAE 75W-90 Synthetic Gear Oil. Capacity: ~3.6 quarts.

The front and rear differentials on the 2023 Sierra 2500HD specify a full synthetic 75W-90 gear lubricant. For models equipped with the G80 automatic locking rear differential, no special limited-slip additive is required. Always use a high-quality synthetic fluid to protect the gears under the heavy loads these trucks are subjected to. Typical change interval is between 50,000 and 100,000 miles, but inspect sooner if the axles have been submerged in water.

Brake & Power Steering Fluid

• Brake Fluid: DOT 3 Motor Vehicle Brake Fluid.
• Power Steering: The 2023 Sierra HD uses an Electric Power Steering (EPS) system, so there is no hydraulic power steering fluid to service.

Brake fluid should be flushed and replaced every 2-3 years, regardless of mileage. As a hygroscopic fluid, it absorbs moisture from the air, which lowers its boiling point and can cause corrosion in the brake lines and calipers. Use only new fluid from a sealed container.

Other Fluids

• Windshield Washer Fluid: Use any quality all-season washer fluid, preferably one rated for protection down to -30°F to prevent freezing in the lines and on the windshield.
• Diesel Exhaust Fluid (DEF) (Duramax Only): Must be API certified and meet ISO 22241. Look for this specification on the packaging. Capacity is 7.3 gallons. DEF is a consumable fluid that is injected into the exhaust to reduce NOx emissions. The truck will provide ample warning before the tank runs empty. Never put anything other than fresh, high-quality DEF into the DEF tank.

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