Just Say No to Abuse Declaring War on Terrorism. They are also comparably priced to EG-based antifreeze. Even greater protection can be obtained by using a higher concentration of antifreeze to water. Before safer PG antifreeze was introduced, all antifreezes contained approximately 95 percent ethylene glycol, a highly toxic chemical that if accidentally ingested, attacks the kidneys and can cause irreversiable damage.
Many manufacturers recommend changing antifreeze every year.
When converting to PG antifreeze, all EG must be drained entirely and the cooling system flushed, since mixing PG and EG would negate the added safety. Used antifreeze, which also contains metal contaminants, always should be disposed of properly to avoid accidental ingestion, seepage into underground streams or other water sources. Many automotive parts stores will accept used antifreeze for recycling. Walk dogs on leashes and supervise them closely when they are outdoors. If you know or suspect your pet has ingested EG antifreeze, take the animal to a veterinarian immediately.