Auto Fluid or Gear Oil

I've had pretty good luck with just plain 80-90 so far on mine. I was even bad the first time and probably filled it with rear end oil if I had to guess, but it didn't seem to care much. After I knew about the difference between rear end and standard oil I went a little different direction the second fill. The store was out of plain 80-90, only had gear oil, so I got the thickest plain motor oil I could find (50wt, can't remember if it was 20-50 or something similar) and put two bottles of lucas stabilizer in it to thicken it up. So far it doesn't seem like it's any different than plain gear oil. Took it a little while to mix up good (used to shift hard below 30 odd degrees), but it's pretty consistent now. Just don't try pouring a bottle of lucas down a funnel when it's under 20 degrees outside, literally took over a day to fill...