Hydraulic System

[Skippydiesel]

I am, trying to resurrect a Hustler Super Z. Taking small steps as I don't want to invest too heavily, before knowing what the outcome will be.

I am nearly ready to test the hydraulic transmission. It had been leaking badly, so oil level is well below specified "1in from the top of the reservoir". There may not be sufficient oil in the reservoir to operate the transmission without cavitating.

I would like to top the reservoir up to the correct level but don't know what oil has been used. My (old) Operator Manual specifies "SAE 10W-40, SG, SF/CC, CD service motor oil". This is a very old specification - almost unavailable in Australia.

My intention is just to test the transmission works okay and then drain all the existing oil, replace the filter and refill with a suitable current oil - Hustler 15W-50 synthetic

Will it be okay to use any 10W - 40 mineral (or semi synthetic) engine oil for a short test run???

 

[ILENGINE]

Skippy you will be fine with modern oils. Oil designation are backward compatible, at least for engine oils. Not so much for gear oils in some cases. Also as long as the main unit is full of oil, the reservoir is just an overflow for efficiency loss. Meaning the hydrostat system operates as a closed loop system, and the only oil that is drawn from the reservoir is to replenish what is lost from the pump during operation.

Or to explain a different way. If a hydrostat system is 90% efficient. If you put 1 ounce of oil into the system that circulated between the pump and drive. It will complete 9 cycles before being lost and returned to the reservoir.