I run Amsoil 5W30 3000 series full synthetic. With the new hands pumps from Amsoil and fit on the large mouth Amsoil containers, refilling the trans is now easier than ever. Before this pump came out, filling the 5600 trans was a pain in the neck. I think the pumps retail between 10 and 15 bucks and are totally reusable. Just note that these pumps won't screw on to standard size quart bottles with the small caps, just the larger Amsoil bottle caps. OMG I'm sounding like a salesman... .