Hi D.
John Deere has a product called Cool-Guard with a service life of 5000 hours. It is available in 50:50 premixed or concentrate. I usually recommend the premixed because you can be assured of having good quality water and avoid possible warranty issues that can arise from using water of questionable quality. Also its more convenient for top-off. The part number for a 2.5 gallon container of pre-diluted is TY16036. When you change check to see if you can see deposits in the radiator and if you do then use a fast-acting flush. After you have drained the flush then change water at least 3 times and better yet 4, allowing it to reach operating temp each time and with the heater valve (if so equipped) wide open. Then you can add your new coolant and you should be in good shape. The Deere dealer should be able to give advise about adding the inhibitor.
Good luck
Mark
