tommyg 152 #1 Posted November 6, 2016 I know I've seen posts regarding the best oil to use in the hydro system of the D series, but I can't find them. Anyone have anything thoughts or can point me to those threads. I'm using a synthetic 10W30 and it works OK, just seems like the system whines more than it should under load. I have a low tolerance for stuff like this. Anyone? Share this post Link to post Share on other sites
squonk 38,848 #2 Posted November 6, 2016 (edited) Mobil 1 High Milage Edited November 6, 2016 by squonk Share this post Link to post Share on other sites
pfrederi 17,129 #3 Posted November 6, 2016 I think they all whine to some extent, mine does some whining on regular dead dinosaur stuff. Share this post Link to post Share on other sites
Macgyver 90 #4 Posted November 14, 2016 I have two 520H. Have changed both to. 10 w30 Mobile 1 syn. I will say that both are quieter & seem to pick up faster when cold. Share this post Link to post Share on other sites
