Cedar Post: Does Any Product Really Work to Retard Rot?

I have cedar posts that have been in use in the garden for 15 years. I treated them with Green Cuprinol:

Seal the end with tar. Roofing tar should work OK. Dig the hole 1 foot deeper and have the post rest on top of gravel. The post should last 15 years or perhaps many more. My mailbox post is going on its

Thanks to all. I have a gallon of Behr Post Protector (similar to the Cuprinol) home but will consider the tar idea which makes a lot of sense also. (Why not apply the roofing tar up the sides of the post as well?) Thanks again! Frank P.S. At Home Depot, is that called Roof Sealer?

Frank-

How about a metal post base where the wood is slightly ~2" above the dirt?

cheers Bob

According to frank1492 :

Caution: coating the bottom of the post with tar will prevent the bottom of the post drying out, and will accelerate rot. This only works with pressure-applied anti-rot that leaves the bottom of the post still able to drain.

You want the bottom of the post being able to dry. That means using materials that _don't_ seal the wood below grade, and parking the very bottom of the post in something that drains well. Like gravel.

Thanks. I have gone with Behr Post Preservative (Similar to Cuprinol) and will dump some pea stones in the hole before I set the post. How's that for a compromise??? Frank