I just ordered a loop 900 but forgot to get a bottle of thick lube 
i only have thin lube on hand, will it make a big difference in performance if i use thin lube on my bearing? Would it be better to leave my bearing clean, or put an excess of thin lube? thanx!
Do not put thin lube on a looping yoyo. It will make it unresponsive, the opposite of what you want in a looper. Just leave it at its factory setting until you can get the correct lube.
You could just over-lube it, but then you just got a lot of lube in the bearing and it will eventually break down faster than the thick lube.
A lot of people lube their Loop 900’s “2 drops of thick, 1 drop of thin” to get the performance they want. So, it seems that having both on hand might be the way to go.
If it was me, get the thick lube. If your order hasn’t shipped, call the shop and see if they’ll hold your order, invoice you for the thick lube, you pay it fast and then they drop it in the box.
For a looper 3-in-1 or sewing machine oil will work just fine. I actually pack my raiders w/white molly grease.