What are anti-freeze agents, and how do they differ?

Anti-freeze agents for cooling circuits

Coolant additives plus water produce the anti-freeze agent which is filled into the radiator. The coolant additive is a corrosion/anti-freeze agent (concentrate), which contains corrosion inhibitors (approx. 5%), anti-freeze agents (approx. 93%, MEG or MPG) and water. Such agents include:

Monoethylene glycol (MEG)
Synonyms: Ethylene glycol, MEG, monoethylene glycol, ethylene glycol, ethandiol

MEG is generally used for vehicle cooling systems.

The freezing point of this anti-freeze agent falls, depending on the manufacturer, from approx. -10°C to -40 °C with a water proportion of approx. 20 to 50 Vol% and then rises again on further concentration. At maximum concentration, the freezing point is approx. -13°C!


Monopropylene glycol
Synonyms: Propylene glycol, MPG, propandiol

MPG is used in the area of solar systems, heat pumps, in the foodstuffs industry and pharmaceuticals.
The freezing point falls continuously to approx. -59°C at maximum concentration.

Anti-freeze agents for the windscreen washer system

High-quality anti-freeze agents primarily provide cleaning performance, then anti-freeze protection, material compatibility and minimum stress on people and the environment.

The windscreen washer fluid (concentrate) consists of ethanol (approx. 79%) and monoethylene glycol (approx. 8%) for anti-freeze protection and to prevent rapid icing or icing of the nozzles. It also contains anionic and non-ionic tensides for cleaning, the removal of insects and salt in winter. The remainder consists of dyes, scents and water.

The ideal mixing ratio is approx. 30 Vol% windscreen washer fluid and 70 Vol% water, which ensures anti-freeze protection down to approx. -18°C.
If the concentration is increased, this increases the stress on paintwork, front and rear lights, SRF pipes etc. A sufficient amount of water is also required in order to clear the dirt released by the tensides from the windscreen.

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