I use Amsoil 15W-40 in my hydro on a 717A. The operator's manual and the Deere products are inconsistent, if I recall correctly. The product the manual recommends is not an available Deere product. That is how I got myself directed toward the Amsoil 15W-40 products. I've ran them three seasons, changing oil and filter in the off season. I don't run that much, only about 350 hours per season (use the machine less than half of my time, using a w/b the remainder).
The JD requires 8 quarts. It is a huge difference from my Exmark w/b, using 1 quart of Mobil 1, 15W-50.