if you have a 15 lbs cap the boiling point of straight water is 249 degrees which is over the point where I would shut down the engine. We ran our circle track cars with distilled water and Water Wetter with an 22 lbs cap and that engine got over 240 regularly without throwing any steam on the windshield. Water removes the heat from the block better than antifreeze and the Water Wetter helped the water to run cooler without interfering with the waters ability to absorb the heat. The Royal product was not out a few years ago in Canada so the only product available was the Water Wetter. The Water Wetter and Ice will lower the temperature of the coolant