Do you trust the source? As in it's really Castrol oil.
UltraClean is the base level oil from Castrol, it's a semi-synthetic, and the 0W20 should be API SP and ILSAC GF-6, assuming that it's recent stuff.
I don't use the 0W20 viscosity grade, but I have used Castrol UltraClean before in a heavier grade, and it was fine. Assuming API SP is all you require, and you keep the intervals reasonable e.g 5k miles.