I have always run 5W40 full sythetiic. I started out with Mobil Devac1 but last year switched to Amsoil. My oil change interval is 10,000 KMs. Truck has all emissions intact but I run with the EGR unplugged.
I ran mostly Mobil1 5W40 in my 2005, and changed it around 7-8K. But this 2010 tells me to change the oil so often that it doesn't make sense to run synthetic. But I've been doing it anyway. Went to synthetic at around 9K using Schaeffer 5W40. Next time around Royal Purple 15W40. May not continue using syns at this rate. Makes sense in the winter.
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