John Deere 9500 combine oil

[tneibling]

Last year we sold our old 1979 JD 6620 and got a 91 JD 9500. The previous owner told us that he switched the oil from conventional JD Plus 50 to Ams fully synthetic oil. We changed it once last year and used the Ams and it is due again. Dad was wondering if it would be bad to switch back from the Ams synthetic oil to conventional JD Plus 50. I talked to the local diesel shop and they said that it would probably be ok to go to a synthetic blend but not conventional. Dad just wants to get it changed before we run tomorrow so he's going to go get the Ams again.
Could somebody shed some light on this for us?

[StarDriver]

It shouldn't hurt it, the synthetic would be better though. The JD oil won't hurt anything, it is a good oil..

How many hours between oil changes?