IMO all oils are different, WT is just a number with no way to mesure.
CS or Cts(centistroke) is an accurate mesurment but even between companies it can be off.
IMO Kyosho, Mugen, AE and Xray have the best oils and are all close enough that you wont notice the diffrence between 5000cts in each brand.
OFNA and losi are in their own world when it comes to oil viscosity and their ratings.