Outdoor finish for oak

As others have mentioned, the marine finishes of some type would be the way to go. Of all the products at big box stores, none of them will last any length of time at all. Wood moves and therefore creates micro fissures in the surface coat allowing moisture to get behind the finish. At that point it is game over. The marine finishes have the greatest resistance to combat this issue.
I personally avoid a coating of any type for outside unless it is a penetrating type. I usually use https://www.twpstain.com/.
Also, white oak is substantially better at fighting off rot and decay than red oak. White oak is more dense and has a different grain structure than red oak.
 
I would use Linseed oil. It will allow the beauty of the wood to be maintained. Ultra violet light is the killer of all finishes. Varnishes will degrade over time and has to be stripped off or sanded. Linseed oil would only require a new application once a year with a rag, 10 minutes.
I have a garden bench. After buying it I replaced all the wood with composite wood. Tens years no fading, no splinters, no painting , no varnish, no maintenance looks the same as when I bought it.
 
mickri said:
Some people use Cetol (sp?) instead of varnish on their woodwork. It is like a semitransparent paint. It lets some of the wood grain show. 2 to 3 coats to start with followed by a fresh up coat once a year. It goes on like paint. Way easier to apply than varnish but it doesn't look like varnish.
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Cetol works very well even on southern exposure woodwork. I started using it about 20 years ago after doing a lot of research on best outdoor finishes. It's advantage compared to other materials is the fact that it allows moisture to go in and out without peeling and destroying the original material, very unusual in this respect. Also renewing it is easy, just some light sanding buffing and one coat if needed.

It is translucent and it comes in different colors so picking the right color can be tricky. Sometimes I mixed 2 colors to get something that was more pleasing to me.

It is a system of 2 materials Cetol 1 for the 1st penetrating layer and Cetol 23 for the 2nd and 3rd layer. The company is trying to use the Cetol name recognition in marketing other products so pay attention, for example Cetol SRD is not the same product etc.

Ariel
 
I should have mentioned using linseed oil will require a drying or flash off time of about a week, before you'd want to sit on it.
 
DiscoDan said:
My father build me a porch swing out of Oak. She originally finished it with polyurethane which did not last. I sanded all of that off and tried tung oil but that only lasted a season. I saw in a Woodworking magazine someone used deck stain which makes some sense. Is there any other recommendation for a durable finish that can take the elements for more than a season?
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Dan:

Since your post is several weeks old, I suppose you have already decided what you want to do as far as finishing your outdoor oak porch swing.

But if not, you may find the latest video by YouTube creator Marc Spagnuolo (the Wood Whisperer) helpful. It is about his experiences with various finishes on outdoor furniture and other outdoor structures.

He presents some logical conclusions on what to consider when choosing a finish, and uses a number of examples - various pieces of furniture under various conditions, using several different finishes.

Bill
 
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