My wifes 99 Nissan Altima (4cyl, 2.4L) is currently running 5W30 Mobil 1 and a pureONE filter. I still have a while before it is due for a change, but I have been looking at the possibility of changing oils. I would like to give GC a shot, but have had a hard time finding it so far. Which oil, and which weight works well with this engine? Thanks