When it has leaked out.
The fluid is not under extreme pressure or heat so it will last many, many years.
All slideouts 'retracted' (closed)---level should be 1" from top of reservoir.
Just top off as needed (if needed) with the same type of fluid as recommended by your slideout mfg. Typically a tranny fluid....ATF +4
Hydraulic System Info.
Is it time for your medication or mine?
2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
US NAVY------USS Decatur DDG31