What one expects and what one might say are highly personal. Personally, I wouldn’t notice or care either way if I was told that oil or oils were on aisle nine be they bath or motor. Both exist as a type of product and as individuals with significant differences and purposes. My impression of the relationship between logic and language is similar to the relationship I have with old coats I find in the back of the closet. I slip them on after I’m dressed; sometimes they fit and sometimes they don’t.