I have a small cabin with cedar lap siding. The siding was put on a couple years ago and has never been treated. The cabin is in the woods; I love the dark grey look of weathered wood--the cedar is graying nicely but I want to make sure it's protected.
The people around here tell me to treat it with motor oil. Several of them have used a mixture of used motor oil and--transmission fluid?--on their homes. It certainly seems to last and protect the wood.
I couldn't find much online about treating cedar siding with motor oil. A few vague references to used oil being a carcinogen, and lots of talk about preserving the original color of the wood. Since I'm not interested in preserving the original color and like it naturally weathered, would motor oil be a good option? If used motor oil is bad, what about unused?
I have built a couple of buildings and used cedar lap siding. I used the rough sawn stuff, and got a water repellent stain in a grey color close to the color of weathered cedar and used that as a finish. I don't trust used motor oil--doesn't penetrate, is messy, and contains bad stuff. I have seen some home made wood stains/preservatives that use parafin wax melted and mixed in as a water repellent. I like the use of a water repellent finish, clear or a stain, to help keep the wood from absorbing as much moisture--should extend the life of the wood a lot. A clear finish will allow natural weathering and greying of the wood, might slow it down a bit, but I decided that using a grey stain got the wood started out looking grey and where it weathered fastest it still looked grey and where it didn't weather, well, it was still grey from the stain. I should probably restain my current garage, it's been 10 years or so, and there are some uneven looking spots. Nothing very critical though.
My MIL's cypress house was done with diesel fuel. when I heard that I thought it was the dumbest idea EVER! Uhh wood + fuel/ to many chances for a huge fire! ask alstate what they think! By the way I had to replace LOTS of wood on her house after only 15 years, it looks like a shack.
I use Thompson water seal and a garden pump up sprayer, cover windows plants ect. and be done in a few hours! add some stain to it, I think you could.
Good luck and I would stay away from motor oil or anything like it!
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When I built my barn, I used 2x6 T&G, treated for the bottom 4 feet and 1x12 pine for the upper siding. The barn is 100' by 100'. I didn't want to paint it, so gave everything a good coating of Thompsons waterseal. Two years later, it needed it again. At $60.00 for a 5 gal bucket and a thursty barn, I knew I'd have to do something different if I were to preserve the fresh wood color. My neighbor had built a shed/garage and sided it with pine. After several years, his looked like new. I asked what he used to preserve it and he was simply using non-detergent motor oil. Not used oil, but new. He prefered hydralic oil. It was lighter, went on smooth and he had a cheap supply. I tried it and found it lasts 4-5 years. Isn't any more of a fire hazard than Thompson's. Soaks in and isn't oily on the surface. I try to do it on a hot day when it is dry out, soaks in faster and less run-off.
I would think that Cedar siding would benifit by an oil treatment. Since the siding has already discolored, that wouldn't be a concern.
As far as diesel fuel or used oil, i think I'd stay away from that.
If you are dealing with new siding, and want to retain the color, the best way (in my opinion, based on years of selling paint products and solving customer problems) is to use a real penetrating stain, tinted to the original color, and containing a water repellent and if possible, a UV filter compound.
I use a linseed oil based product on my unpainted siding. It will certainly preserve the wood and does little to mute the graying effect (or whatever color your wood siding takes on). The challenge is that it's like painting with water, but a spray application is just not as good as a brushed treatment. Best wishes in whatever you choose to do.
Motor oil thinned with paint thinner about 50/50-Will soak right into the lumber--I don't like the smell of Used oil or the Dark Look, but I used it on a tree house. Took months before the Smell was gone. New oil---Don't notice a smell in a few days ofter usage---keeps new wood looking natural for a long time. Randy