I have an oak dining table that is made of horizontally laminated blocks, not "butcher block" since the end grain is not at the top. It had a natural oil finish. Over the years it has been used mostly at one end and has accumulated a layer of "crud" visible in the photo as a dull spot.
This picture is after vigorous scrubbing with Murphy's Oil Soap and a soft rag. If I run a fingernail across the dull area I scrape up quite a bit of crud that feels oily/waxy. I don't get anything when doing the same over other areas.
Given that the oil soap/soft rag does not seem to help, what's the next step? I feel like something very mildly abrasive, like a plastic scrubber sponge gently applied, would probably remove the crud but don't want to damage the wood.
What's the best way to remove the accumulated crud, and what should I apply afterwards to restore the original look?