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What kind of oil does a 6.6 Duramax diesel take?

The standard answer is Dexos1 Gen 2 5W-30 full-synthetic oil. This is the typical requirement for most modern Duramax 6.6L engines, though exact specs can vary by model year and climate.


The Duramax 6.6L has evolved across generations, and the oil specification can differ depending on the engine's year, region, and driving conditions. Always verify with the owner's manual or GM service documentation to be sure you’re using the correct oil for your truck.


Oil specifications by generation


Key guidelines for the Duramax 6.6L across generations are outlined here. Always rely on your specific vehicle manual for the final specification.



  • Oil must meet Dexos1 Gen 2 certification, which is GM’s modern standard for many Duramax engines.

  • Viscosity is typically 5W-30 for most climates and usage patterns; follow the viscosity recommended in your owner's manual for extreme temperatures.

  • Oil can be either full synthetic or a synthetic-blend, as long as it carries the Dexos1 Gen 2 designation.


In summary, for most current Duramax 6.6L applications, Dexos1 Gen 2 5W-30 is the baseline specification. Older or special-duty models may have different requirements, so always confirm with official GM documentation or your dealer.


Choosing the right oil for your Duramax


To ensure you select oil that meets GM’s standards and your warranty requirements, follow these steps:



  1. Check the owner’s manual or the inside cover of the service manual for the exact Dexos specification and viscosity recommended for your vehicle’s year and model.

  2. Look for the Dexos1 Gen 2 (or Dexos1 Gen 2-compatible) certification on the oil bottle; avoid oils lacking the Dexos designation.

  3. If you’re unsure, ask a GM dealership service advisor or a qualified diesel technician to confirm the correct oil specification for your truck.

  4. Consider your climate and driving habits (towing, heavy loads, extreme temperatures) and choose an oil viscosity that aligns with GM’s guidelines for those conditions.


Following these steps helps ensure you're using the right oil and maintains warranty coverage and engine longevity.


Summary


For the modern Duramax 6.6L, Dexos1 Gen 2 5W-30 synthetic oil is the standard recommendation. Always consult your specific vehicle’s manual to confirm Dexos specification and viscosity, as older generations or special-duty configurations may differ. When in doubt, verify with a GM dealer or trusted mechanic to ensure compatibility and performance.

Is rotella 15w40 synthetic good for diesel engines?


Yes, Rotella is a heavy duty diesel truck oil. Since it is a diesel truck oil it retains the high levels of zinc phosphate additives we like for our motorcycles since diesel don't have catalytic converters.



What oil is recommended for 6.6 Duramax diesel?


GM recommends a 15W-40 viscosity grade engine oil in all instances that the ambient temperature remains greater than 0° F. If the ambient temperature is below 0° F, a 5W-40 engine oil is required to maximize protection during cold starts and the engine warm-up period.



How many gallons of oil does a 6.6 Duramax take?


Duramax Fluid Capacities

YearEngineCapacity
2017-20196.6L Duramax L5P3.17 quarts
2017-20196.6L Duramax L5P31.5 quarts
2017-20196.6L Duramax L5P7 gallons
2020-20246.6L Duramax L5P10 quarts



What oil does a 6.7 l turbo diesel take?


Materials

NameSpecification
Engine Oil - SAE 0W-40WSS-M2C171-F1


Kevin's Auto

Kevin Bennett

Company Owner

Kevin Bennet is the founder and owner of Kevin's Autos, a leading automotive service provider in Australia. With a deep commitment to customer satisfaction and years of industry expertise, Kevin uses his blog to answer the most common questions posed by his customers. From maintenance tips to troubleshooting advice, Kevin's articles are designed to empower drivers with the knowledge they need to keep their vehicles running smoothly and safely.