How important is the surface tension of an engine coolant?

Surface tension is the force on the surface of a liquid that tends to diminish the surface area to a minimum. The surface tension of Evans is less than that of water.

The scale that surface tension is measured in is dynes/centimeter.

Water has a very high surface tension (72 dyn/cm) that makes it a poor choice for an engine coolant. A mix of EG and water (50/50) has a typical reading of 56 dyn/cm, while Evans is much easier to release at 44 dyn/cm.

When nucleate boiling occurs bubbles are formed in order to carry away the heat to the cooler liquid in order to re-condense.  The cooler engine coolant can then flow on to the hot metal surface to repeat the process.  If the engine coolant surrounding these bubbles has a high surface tension then this movement is resisted.

With Evans in your cooling system, this process is unhindered by high surface tension and can easily flow and be released from the metal surface.

Surface tension is an important factor in engine coolant selection.

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