Can I put Prestone power steering fluid into a Buick Enclave? Or does it require OEM fluid?
OEM fluid is almost never required - you can almost find an aftermarket fluid meeting the same spec. Look on the fluid and look for "Meets GM Spec 89201184" or something simmilar. As to what you need specifically:
The Enclave requires either Dexron VI or equivalent or GM 89021184 or equivalent fluid. It depends on the year it was built.
Amsoil has a lookup you can use to find fluid compatibility: http://www.amsoil.com/mygarage/vehiclelookuppage.aspx?url2=2015+BUICK+ENCLAVE+D
Of you can download the manual for your year Enclave here: http://www.buick.com/owners/manuals.html and find the fluid spec.