Guys, I just went to napa to pick up some oil and filters. They told me Rotella 15-40 is being phased out and being replaced by Synthetic. I have only run Rotella in my 2 trucks and do not want to change, but if Rotella is being phased out which oil should I change to? I know there will be lots of differing opinions, but I want to stay with similar specs. as the rotella as it has served me well.