Removing stains on cabin sole

[Sadlermike]

I have stains in short (300mm) sections of the white insert on my teak and holly cabin sole. Gentle sanding has not removed these. What are my options, please?

 

[Evadne]

Bleach (Oxalic acid)? "Astonish" stain remover would be my first attempt, it rather depends on what the stain is, organic or inorganic, etc. Mildew and white wood - should be removable. Engine oil soaked into the wood - you may just have to live with it.