It was time to winterize my 1986 Toyota Pickup, so I brought it to a friend of mine who's a mechanic and asked if it would make sense to use pure anti-freeze in my radiator instead of mixing the coolant with water. He said that would be fine, and it seems to me that if a coolant solution does a good job, 100 percent anti-freeze would be even better. Still, I noticed that my owner's manual says to use half anti-freeze and half water. Who is right?
Who are you going to believe, the engineers who built the truck or your buddy?
You should never use straight anti-freeze (ethylene-glycol). It can actually boil at a lower temperature and freeze at a higher temperature than the glycol/water mixture.
If the owner's manual says 50/50, that's what you use. Go back to your mechanic and tell him to drain the coolant system halfway, and then fill it with water.
Please, keep all pets away from anti-freeze.