In fact, standard HyGuard causes problems with the hydraulic system when temps are below 20F. Your 350 has the same Cessna gear pump that Ford, IH, Oliver, Allis Chalmers, Case, etc. Yes, Deere will tell you to use HyGuard - but that's not based on any special need. In the hydraulic tank, you can use any 20W hydraulic oil. If you have replacement sealed rollers, the HuGuard is fine -except if they're leaking, they're probably shot anyway. Same grease now is sold as 'corn head' grease. that is what Deere was recommending - but sold it as 'track and roller' grease. It's the best compromise and it won't leak out of worn seals.

If you have any original rollers, or track idlers, I would NEVER use Hyguard, even though Deere used to recommend that or 90W gear oil. Many other companies sell oil just as good, but at least with the Deere brand, you can be sure. The reverser only holds 3 gallons, has wet clutches, and it is extremely expensive to fix if something goes wrong. With the reverser - if you have one - only use a combo trans-hydraulic oil and my choice would be to use the Deere brand HyGuard. 90W GL-5 will give just as good protection and is less apt to leak. I use it here in NY, but don't use my crawler in extreme cold. If I lived in Georgia, I'd be using the 90W. Deere also was shooting for one 'fits all' oil for their ag, forestry, and industrial line. Deere started recommending type 303 or HyGuard because it gives better all weather protection, especially in extreme cold temps - and 90W gear oil does not. Many owners prefer and use EP 90W, GL-5 gear oil in the trans and final drives - if a 350 or 350B.

John deere 350 dozer oil filter