Detach the hose from the side of the reservoir body and plug the
reservoir fitting after the old oil drains from it. Then put the now
loose hose end into the waste can, replace the paper filter and refill
the reservoir with new fluid. Start the engine and the pump will suck
the new fluid into the steering system. Keep refilling to avoid any air
from getting pulled into the system.
Don't forget that you can kill the engine with the STOP lever on the
I have no preference about the fluid, call MBUSA and ask for "Technical"
if you're in doubt; they'll give you the official recommendation.