I don't think it gives any antifreeze protection, or very little.
Don't know how it affects the heat capacity or heat transfer rate,
but I suspect that the oil film it will leave on the metal may hamper
heat transfer somewhat so if you have any tendency to overheat this
may make it worse.

Antifreeze is toxic if you drink it in quantity, but it is not very toxic
other than causing dehydration. It is not like lead, cadmium, mercury or a
lot of things that are very toxic in small quantities.
I would not hesitate to use it. The antifreeze that is really toxic is not
longer used as such, i.e. methyl alcohol or methanol.
(also hard on paint, etc.)
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma