Calculates how much coolant needs to be removed and replaced with antifreeze or water to achieve a 50% mixture of water and ethylene glycol antifreeze. Just enter the vehicles cooling system capacity and the reading you get for the freezing point of the coolant (using your hydrometer or refractometer). The app will calculate exactly how much coolant to remove from the system and whether to top it off with 100% antifreeze or water. Save money and time by getting it right the first time and not wasting expensive antifreeze. Designed for use with ethylene glycol antifreeze. Most vehicles use ethylene glycol. Pet safe non-toxic antifreeze is the exception to this as it is propylene glycol and this app is not designed to calculate correction of those systems. Always use antifreeze and water which meets the manufacturers specifications and follow all safety and service precautions. Do not attempt to test, service or repair the cooling system when it is hot as it can cause severe injury. Always follow up all corrections by running the engine, allowing it to cool and verifying the proper mixture and freezing point.