I use Royal Purple 10W-30 and completely change oil and filter at 6K. I have 42,260 miles on my 2010 T/C 4.0L and just noticed no oil on the dip stick with less then 5K since my last oil change. This is the first time I've ever had this happen with any of my vehicles I've owned which have all been new and too many to mention. I'm going to change oil and filter and watch closely. The dealership I purchase from I used to work at and know them very well and I will follow up with them.