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Description
Truck mods are great, but long-term reliability always comes back to one thing: proper maintenance. Using high-quality oil, along with filters specifically designed for your fluids and powertrain, goes a long way toward delivering hundreds of thousands of dependable, trouble-free miles. Keeping up with the correct service intervals and running the right fluids is key to protecting injector health, maintaining cooling system efficiency, and maximizing overall engine life, especially on higher-mileage LLY/LBZ trucks.
Factory Fluid Capacities & Recommended Weights
Engine Oil (6.6L Duramax)- Capacity: 10 quarts (with filter)
- Recommended Oil: 15W-40 diesel engine oil
- Cold Climate Option: 5W-40 synthetic
- Service Fill: 7.4 Quarts
- Total Capacity: 12.7 Quarts
- Recommended Fluid: Allison approved TES-668 or TES-295
- Capacity: 5.8 quarts
- Recommended Fluid: GM TranSynd Full Synthetic
- Capacity: 2 quarts
- Recommended Fluid: Dexron III ATF (Manual Shift) Auto-Trak II (AutoTrac)
- Capacity: 1.75 quarts
- Recommended Fluid: 75W-90 gear oil
- Capacity: 3.2–4.3 quarts ( Varies by model year)
- Recommended Fluid: SAE 75W-90
Proper filtration and OEM-spec fluids help protect critical components like injectors, turbocharger, and transmission while extending the life of your Duramax.