First oil change on new Ram.

My 16 Ram 3500 Diesel states 15,000 miles and it is NOT synthetic. I did my first at 4500 and my 2nd at a little over 6000 later. Not sure I'll ever be able to go 15000 between changes even though it's a fairly expensive oil change. BTW, the new Cummins diesel oil filter is a PITA to change. Can't get to it from the bottomside. Have to take it out the side through the front wheel opening.