some years ago we clear coated the log siding and deck overhang w/Flood CWF UV oil finish. Am now power washing and then on to a final cleaning/sanding etc. What is best product to use for longevity and will all the old finish have to be removed (which will be impossible w/out sand/soda blasting) or will the new coating stick to old? This is up in northern Minnesota with winter temps at -40. Appreciate all the comments
It sounds like the product you used before worked well. You should be able to apply it over what you have but remember the new layer will trap any dirt.
A mix of 1:1 processed, not raw, lindseed oil and mineral spirits, paint thinner or similar solvent makes a decent sealer but will not have the UV protection. Search for a post on this site by a person who has used it for over 50 years on a cabin.
There are several good products out there but the best is from Structures Wood Care nature color (oil-based) or Natureone (water based). Both will adhere to existing coatings provided the existing coatings have good adhesion to the surface.
Under eaves and areas not exposed to the sun will be hard to remove without stripping our sanding. So keep in mind that whatever color stain you put of the top of your logs it will be influenced by what color is underneath. It may require you a bit of creativity to make sure your stain is even.