July 14/15

18,000 Miles (30,000 Kms) - Oil change interval

'04 GMC Sierra 3500 6.6 L Duramax Diesel


Yes, you read that correctly.  

In June of 2014, I had run 14,780 miles (23,800 kms) over the course of 12 months and had the oil tested by a local Caterpiller Tractor dealer at their oil analysis lab.  The results were great.

In July 2015, I had extened the interval yet again (as per my headline above) and had the oil tested at the same facility.  Again the oil is fine.

For my truck application, I use the Amsoil 15W40 Diesel & Marine as recommended by Amsoil.


I also used the Amsoil EA Oil filter which is rated to 25,000 miles


If you are not sure about what Amsoil products to use in your application, follow this link.



Test results on the oil analysis are below.

Test 1


Finning test

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