The parent's van, a 2005 Dodge Grand caravan with 75000 miles on it, has never had the transmission serviced. I'm taking over service on it now. Before it just had whatever the wonderful techs at Walmart thought it should have. I was going to start with a pan drop and then a few miles later a full fluid exchange. I've been looking at the visc and other specs of Amsoil universal against most ATF+4's. It seems like the Amsoil looks to be thicker and has a lower VI. I was going to use Amsoil just because it is available locally and this van gets run what I would consider severe service. Should I just go with a good ATF+4 or will the thicker Amsoil work? I also have some Lubegard laying around so I'm debating whether to add some of that in too or not.