If I remember correctly, J20C is the universal spec for Tractor Universal Premium Hydraulic Oil. If the manual specs gear oil for the trans / HST it is in error.
J20C is the spec for "Universal premium hydraulic oil". The Mahindra 3525 is pretty forgiving, concerning the hydraulic oil specification, but we use J20C for all tractor applications (including my Mahindra 3505). The square plug behind and to the right of the seat is both the check and fill...
Your 2004 Mahindra 3510 should have a "X" in the serial number (3510X.....). I have seen a couple of 10 Series Mahindra tractors that were "transitional" tractors manufactured in 2001. They had "old" running gear (chassis) but "new" sheet metal. IIRC, all 10 Series were manufactured by Tong...
Our homestead is "out in the country" where power outages are common. We also have five people sharing the benefits of a 40 gallon electric water heater. A tankless L.P. water heater is in our plans in the near future. We have never owned a tankless and any input would be appreciated. Such...