Help me pick- ZT mower maintenance

Ok, thanks for the reply. I have a Cub Cadet ZT2, I have more clearance than you do by the looks of it, so I will go with the 3600 and Rotella T6.
T6 is a great oil. However, I have a very dusty environment, so in addition to changing my air filter yearly regardless of hours in service, I’m going to switch from Amsoil Small Engine oil to HPL. It’s only 2.5qts in the Kawi engine, and a gallon for the hydros, so IMO it’s only a small financial impact to switch, but the benefits will be measurable.

I’m seriously considering doing UOAs not only on the engine but also both hydros, just to get a baseline. I’ve got the 20w50 Amsoil hydro fluid in it. I will let you guys know what @High Performance Lubricants recommends!
Sounds like a sweet mower! Pics? I've seen some crazy hours on Kawi OPE engines used in various applications. Same with Kohler and Briggs for that matter. A little advice on the ZT3100's. When it's still new, break the fill plugs loose on each drive, apply some anti-seize to them and re-install. They are in there TIGHT. These units drain out when the filters are removed.
That is a really good suggestion!!