For me i am not technically competent in EO and stuffs, so i will always use the same brand of EO.
But i think different viscosity is ok because it only affects how thick your EO will be.
Mobil 5w30 (less thick) + Mobil 5w40 (thicker) = still Mobil, just that after mixing, the EO thickness will be btw w30 and w40?
Having said that, i will still try my best to use the same brand and same thickness la...