GregH said:
As far as mink oil-I use my boots for backpacking in the Sierra's and I've seen boots treated with mink oil soften up so that the boots lose lateral support and also soften up so that sharp rocks start tearing the leather. In addition you start having leaks at the seams from where the stitching is when crossing multiple streams. When carrying a 75 lb. pack up and down rocky trails you need stiff lateral support. Add in crossing streams and snow-I wouldn't use it.
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I'd love to hike in the Sierras, Greg!
I can see where the softening would be a problem for support. We only hike in Gore-Tex boots and haven't had problems with the seams and leaking, but only treat 1-2 times a year with mink oil so I bet more applications could cause the problems people have mentioned. Ivan has a go-to pair of Vasque Sundowners that have been bulletproof and my Merrells are similar.
I looked in the gear cabinet and the spray stuff I used (and complained about) was Silicone Water Guard by Sno Seal...fine for my inexpensive Ariats and easy to apply.