I've got a JD X595 in which I use Amsoil from front to back since it had 25hrs on it. Last winter at about 175 hours, I blew a hydraulic line. When I told the dealer that I had Amsoil in the transmission and that I wanted him to re-fill it with Amsoil when he was done, he just about had a caniption fit!
The usual, you can't use that oil, if you ever have serious trouble, we'll have to send a sample to Deere before we honor your warranty, etc, etc.
My replies were: 1)If I ever have serious trouble, I'll send the sample to Deere for you, and to a third party lab also.
2)Can you please put that in writing on your letterhead so I can send a copy to Amsoil and to my lawyer? No, I don't want to do that!
3)Then I said, why don't we go one step better than that? I have some virgin stuff in the truck, why don't we send it to Deere right now and have them tell you and I why I CAN'T use this stuff? He said John Deere won't do that. Well if they won't do that, then on what grounds are you telling me I can't use the stuff? Needless to say, that was the end of that conversation.
4)Tell the dealer that when you bought your tractor, you didn't buy it from a company that makes chocalates or tuperware or any of that kind of stuff, so why would you buy your lubricants from a company that makes farm equipment?
When the dealer was done repairing the hydraulic line he did replace the hydraulic oil with Amsoil, which I supplied.
Put your foot down, it's YOUR tractor! Don't let the dealers scare you.
Good Luck!