Quoting Removed, click Modern View to see
John Deere Hy-Guard or a UTHF that meets john Deere's JDM J20C spec. Not
plain hydraulic oil or any oil saying it is 303.
You need to invest in at least the Operator's Manual John Deere publication number OMT81347. It will have the info you need for regular maintenance/service of the machine and adjustments.
The 450E has a two book Technical Manual set. TM1330OP for testing and systems info then TM1330RE for the actual repair work (they are sold separate. You can buy manuals from the JD construction and Forestry book store; https://www.johndeeretechinfo.com/
. You might want to watch eBay for those Technical Manuals used. You are looking at $325 to $375 from JD for new depending on electronic or printed, I know that first hand.
The parts catalog (publication number PC2036) is free to use on line at https://www.deere.com/en/parts-and-service/parts/
, if you don't want to buy one.