6.6L Duramax Fluids Guide

Duramax Engine Oil, Transmission Fluid, Axle Fluid, Coolant Guide


The following information is available in the factory supplied owner's manual (or in some cases "Diesel Supplement" manual). If you have lost/misplaced your manual, you may use the fluids guide provided below. It is extremely important that you use fluids that meet or exceed GM's requirements. Deviation from factory recommendations may result in reduced engine life, performance, and/or reliability. Additionally, do not mix fluids of different specifications.




Oil/Fluid Requirement(s):

Engine Oil (2001 - 2006):

SAE 15W-40 recommended for most operating conditions. 10W-30 acceptable for temperatures above 0 degrees F. 5W-40 may improve cold starts in temperatures below 0 degrees F.

Engine Oil (2007 +):

SAE 15W-40 recommended for most operating conditions. 5W-40 may be substituted in temperatures below 0 degrees F to improve cold starts.

Engine Coolant:

50/50 mix of drinkable water & DEX-COOL coolant.

Brake Fluid:

Delco Supreme II or equivalent DOT-3 brake fluid.

Clutch Fluid (5 speed):

GM part # 12345347 or equivalent DOT-3 brake fluid.

Cluth Fluid (6 speed):

GM part # 88958860.

Power Steering Fluid:

GM power steering fluid.

Manual Transmission Fluid (5 speed):

GM Goodwrench synthetic manual transmission fluid, GM part # 12346190 or equivalent SAE 75W-85 GL-4 gear oil.

Manual Transmission Fluid (6 speed):

TranSynd synthetic transmission fluid, GM part # 12378515.

Automatic Transmission Fluid (2001 - 2005):

DEXRON-III automatic transmission fluid (ATF).

Automatic Transmission Fluid (2006 +)

DEXRON-VI automatic transmission fluid (ATF).

Front Axle:

SAE 80W-90 axle lubricant, GM part # 1052271 or equivalent.

Rear Axle:

SAE 75W-90 axle lubricant, GM part # 12378261 or equivalent.

Transfer Case:

Varies greatly by year and transfer case type (manual shift or auto shift). Refer to your owner's manual for the correct fluid for your application.

Transfer Case (2011):

Dexron IV automatic transmission fluid




































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