Here is the situation: an automobile mechanic is suspected of having routinely changed oil, and because most machine shops have oil staining the floor, a new customer walking into the shop would expect a dirty concrete floor that has been stained with oil. Shockingly (bear with me), the mechanic's floor is oil free, both in the past, and in the present. In a story written in the past tense, would it be correct to say: "The concrete floor had never been stained with oil."
I think so, yes. I would instead it put as "The concrete floor was free of oil stains." but that's not really an answer to your question.
haha thanks, and yes, yours is much more direct. Someone told me they thought it could mean that the floor became stained at that moment, or soon before it, as if there was an invisible "until now." Other people didn't have a problem with it, but it made me question.
But, yeah, I agree with @ChickenFreak saying "it was free of oil stains" rather than it had never had them. It kinda makes more sense to me.