Title says it all. I wrecked my open diff (had a slow leak and ran it too low...I know, stupid on my part), but fortunately I found a LSD one for a good price and had it shipped. The only problem is I can't find straight 90 weight oil anywhere. I've tried two NAPAs, two Advanced Auto Parts, Auto Zone, a Toyota Dealer, a Ford Dealer, the local Farm & Fleet, a transmission shop and even an Exxon Mobil distributor. Is there another oil I can use? Suggestions are appreciated.