I was unable to find any reference on the site to this data, so I figured I'd add it. Those of us with silicone radiator hoses need to be aware that those hoses are 15-20 times more permeable to water than epdm (rubber) radiator hoses. A study done by Gates in heavy equipment found that an average epdm hose equipped truck would lose 1 qt of water per year through the pores in the hoses. The same equipment with silicone hoses would lose 20 quarts of water in the same timeframe. Only water is lost, the glycol remains in the system. If one were to top up with coolant or 50/50 mix, it will disturb the ratio and will end up with more glycol than water in the system.