HWH Leveling Jack Oil?

[Jeff August]

What type of oil is for this? I have found in files or database or
somewhere it says strait 5-10 weight or transmision fluid, these fluid
are not the same I beleive. If we had books for this thing I wouldn't
have so many questions.I can't see any fluid in the tank, no dip stick
(except me) but the jacks seem to work OK.
Thankyou
Jeff& Michelle August
1980FC35RB
Plymouth Wi.