Okubo algebras and valuations

If the enveloping central simple algebra of an Okubo algebra comes with a valuation, then we can compute the residue of that Okubo algebra, at least as a vector subspace of the central simple algebra. We give a criterion for the residue of an Okubo algebra without nonzero idempotents to be an Okubo algebra. We also prove that Okubo algebras without nonzero idempotents over a field of characteristic 3 are always the residue of an Okubo algebra over a field of characteristic 0.