Had a gallon of used coolant that I disposed of thoughtfully. Looking for home made wood preservatives for the posts on my carport, found the following http://acbs-bslol.com/restoration/service-department/d97woodrot/
Commercial Products sold as a treatment for dry wood to prevent further rot are most ineffective against established rot in wet wood. There are two inexpensive and commonly available materials which will kill rot in wood. and prevent its recurrence. First, there are the Borates (Borax, Boric acid mixtures,) which have demonstrated to prevent new wood from rotting and killing rot organisms and wood-destroying insects in infested wood. Second, there is ethylene glycol, most readily available as automotive antifreeze/coolant, For killing rot spores and wood-destroying organisms, nothing works better than ethylene-glycol antifreeze, unless it is antifreeze mixed with borates. Glycol is toxic to a broad spectrum of organisms, from staphylococcus bacteria to mammals.
There is a simple demonstration of all of the above statements. Take a piece of hardwood and drill holes in it that are an easy sliding fit for hardwood dowels. I used a piece of one-inch oak about three inches wide and drilled 25/64" D. holes 7/8" deep in the edges; the holes were an easy fit for the 3/8" by 1 1/2" spiral-grooved maple dowels I had on hand. For each treatment tested, I used a medicine dropper to apply five drops of the material being tested to the rim of the hole so that the liquid ran down the wall of the hole. Here are the results of a test begun December 19, 1987. Water: Within about 30 seconds, the dowel was bound tightly. After about 24 hr., it was easily slid out. Water swelled the dowel and the oak piece, but quickly dried out. Glycol: After about 30 minutes, the dowel was tight. It still is after a month. Glycol antifreeze diffuses into the cell walls and swells the wood permanently. Glycerol: The less hygroscopic, larger molecule, more viscous glycerol took about 8 hours to interact with the cell walls of the wood to make the dowel tight. It has stayed tight.