<VV> What fluid to use in stock 60-64 convertible power top motor?

[Rick Loving]

My powertop is giving me issues like it is low on fluid but I can't seem to
recall what was used to fill it when it was installed. 

I seem to think it used just reg motor oil as opposed to hydrallic fluid but
for the life of me can't remember. 

If it has one or the other and I mix them, do you think it will cause any
issues? 

What was used in the stock GM powertops origially? 

I need to top it off as soom as possible....