פירוש על עבודה זרה 76:13

R. Sheshet wants to prohibit oil cooked by a non-Jew, but R. Safra will have none of it. He rejects three potential reasons for why it should be prohibited. If there had been gentile wine in it, the wine would have ruined the oil.
If the concern is that it was cooked by a non-Jew, oil can be eaten without being cooked and therefore should be permitted.
And if the issue is that the vessels were previously used by a non-Jew, the taste would be a worsening taste, and therefore this too is not a reason to prohibit.