Can you varnish over oiled wood

[myoungpy]

I am putting up wood trim to cover up the hull/deck joint inside my cabin.  I like the color of the wood with only teak oil.   If I change my mind, will the oil affect the finish if I decide to use varnish?

[tomwatt]

I'm going to chime in based on past experience (some years spent working as a paint tech at Sherwin-Williams) that may not be totally applicable to teak oil. As long as the main component is a drying oil (linseed, etc.) then yes (maybe). If it is mineral oil, lemon or any waxy oil, probably no.
I would not recomend it in any case. I can appreciate that you like the color of the wood with the oiled look. It is nice isn't it? In practice I don't know of a good way to keep it that way without repeated oiling or going the varnish route.
I'm sure someone with more practice on this will chime in.

edit/update: Sleeping on a topic is always good for clarifying comments, so here goes: one of the things that seems to confuse people is the nature of varnish. Varnish is oil, modified so that it will harden and dry reliably. Usually it is linseed (flax) oil, but sometimes contains other oils as well. Oiling wood with something other than linseed oil normally involves using a penetrating (but still drying) oil rubbed into the wood - the tung oil craze comes to mind, WATCO Danish wood oil is another (linseed based). A drying oil, once dry, could be sanded and varnished over... any of the non-drying oils (lemon, walnut, etc.) will need to breathe and if varnished over will very likely cause the varnish to become cloudy.
You'd have to put me down as voting "varnish".
Some old master paintings which contain walnut oil are still trying to dry/cure after hundreds of years.