I just hit 4K and decided it's time to switch over to synthetic (Amsoil). I've been running OEM filters from day one, and I'm trying to decide if I should continue to do so or switch to something else now. I know better than to ask what filter is best, as I know those kind of questions can get pretty heated! So instead let me just ask what filer are you using, and have you been happy with it? Just to get an idea. Thanks