I ran my new 2006 to 25000 miles on Rotella 15W-40 then switched to Rotella 5W-40 Synthetic. 1-2% milage improvement and everything seems fine. I'll do an oil sample at 10k probably change around 20K. I use the Fleetguard Stratopore Filters too.
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2006 Quad, Long Bed, 2 WD...