with the new oil minders that adjust the oil life depening on how you have been driving I just go by when it tells me to change it. I do run the rotella T6 that is one of the the extream duty recomended oils and the only time I will change it kind of early is if it comes up "change soon" and I have a longer trip coming up where it would be a pain to change it during. there is no count down on mine, it goes from "oil ok" to "shnge soon" to "change now". I wish it had the % remaining also then I could guage when to change it before a upcoming trip if it is getting close anyways.
Steve