It is about time to do my oil change, you don't want to know how many miles since my last one. I am torn between a fully syn and a syn blend plus additives. I have been told that you still have to change the filter after 5000mi regardless of the oil type. So my question is this; What is the point of getting the expensive 20000mi Mobil one when it still has to be changed after 5000mi? How do the syn blends with additives do against fully syn? And one last question just for fun: How many miles have you guys gone a single oil change, fully syn or otherwise?