2015 Chevrolet Silverado 2500HD — Coolant Capacity & Type

The 2015 Chevrolet Silverado 2500HD holds approximately 16–27 quarts (15–25 liters) of coolant depending on the engine, with the 6.0L gas V8 on the lower end and the 6.6L Duramax diesel near the upper end.

Quick answer

• Total cooling system capacity: approximately 16–17.5 qt (15–16.5 L) for 6.0L gas; approximately 26–27 qt (24.6–25.5 L) for 6.6L Duramax diesel
• OEM coolant spec: GM Dex-Cool — orange/reddish-orange, OAT (Organic Acid Technology), meets GM Dex-Cool specification (supersedes GM6277M) and ASTM D3306/D6210; ACDelco Dex-Cool recommended
• Mix ratio: 50/50 (premix) or 50% concentrate + 50% distilled water; in extreme cold, up to 60/40 (coolant/water) maximum

Capacity by engine option

Notes:

• Capacities are total dry-fill estimates. Routine drain-and-fills may take slightly less if some coolant remains in the block and heater core.
• Always verify on the underhood decal or owner’s/service manual if available for your exact configuration.

Flush interval

• Normal service: Replace Dex-Cool every 5 years or 150,000 miles (240,000 km), whichever comes first.
• Severe duty (heavy towing, commercial use, high heat/dust): Inspect level, freeze point, and pH annually; replace coolant at 5 years/150,000 miles or sooner if contaminated or additives depleted.

GM Dex-Cool is extended-life OAT coolant and does not require supplemental coolant additives (SCAs) on either the gas 6.0L or Duramax LML.

How to refill & bleed

1. Safety first: Engine completely cool. Set heater to HOT. Raise front of truck slightly if not using a vacuum filler.
2. Drain: Open radiator petcock (lower tank) and drain to a clean pan. For a more complete service, open block drains if accessible (each side of the block); Duramax and 6.0L both have block drains but they may be difficult to reach.
3. Close drains: Replace petcock O-ring if damaged. Close all drains snugly.
4. Fill method:
   • Preferred: Vacuum-fill with a cooling system fill tool to minimize air pockets, especially on the Duramax due to system volume.
   • Gravity fill: Slowly add GM Dex-Cool at the surge/expansion tank. If equipped with a bleed screw on the thermostat housing or upper crossover, open it during initial fill and close when a steady, bubble-free stream appears.
5. Initial run: Leave cap off, start engine, idle to operating temp. Squeeze upper hose gently to purge air. Top off at the surge tank as the thermostat opens.
6. Cap and cool down: Install the cap, bring rpm up briefly to ~1,500 rpm for a minute, then shut down and allow full cool-down.
7. Recheck: After cool, confirm level at the “COLD FILL” mark. Verify strong cabin heat and no temperature fluctuations. Recheck level again after the first drive cycle.

Tips specific to this truck:

• The 6.0L’s steam/vent line should flow continuously to the surge tank—ensure it is not clogged.
• The Duramax’s large capacity makes trapped air more likely without a vacuum fill; take extra time burping the upper hose and watching for stable heater output.

Common cooling system issues (2015 Silverado 2500HD)

• Water pump seep/leak: Both the 6.0L L96 and Duramax LML can develop weeps at the pump around mid-to-high mileage. Look for dried orange residue near the weep hole or pulley.
• Radiator end-tank seepage/cracks: Plastic side tanks can develop hairline cracks or gasket leaks, especially on trucks that tow frequently.
• Thermostat sticking: Can cause slow warm-up or temperature swings. Replace in pairs on Duramax (dual thermostats).
• Heater core restriction or poor heat: Often from aged/contaminated coolant or mixing coolants. Only use Dex-Cool-compatible products and distilled water when mixing from concentrate.
• Reservoir cap failure: A weak cap can cause boil-over or loss of coolant. Replace if the system won’t hold pressure.
• Hose quick-connect leaks: Inspect upper radiator hose connections and heater hose quick-connects for crusting and seepage.
• EGR cooler/internal leaks (Duramax): Less common but possible; unexplained coolant loss with white steam from the exhaust warrants pressure testing.

Use only Dex-Cool compatible OAT coolant—mixing conventional green IAT or silicated HOAT can shorten service life and create sludge.

Find a trusted shop on Repairius.