I just picked up a wagon whose rear "Self Leveling System" seems pretty much non-functional. I want to begin troubleshooting this system, but I am unsure what kind of oil to put into the resevoir (@ left front engine compartment).

I understand the stealer may have what I need for $15US per liter. Is there a lower cost alternative while I troubleshoot the leaks? I'll be happy to put what's "ideal" into the system once it's functioning, again.

TIA.