If they are oiled, they will feel ... well ... oily.
All oiled filters I've seen could be cleaned and re-oiled.
The cleanable/resusable dry filters I've seen were foam. If the filter element is white(-ish), it's probably dry, one-time (although a good back flow with compressed air will often clean one out).
But I don't keep up with such things as well as I used to, so don't be surprised if all the above has changed over the years.
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