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How to Mix Propylene Glycol & Ethylene Glycol

by Dale Yalanovsky

Propylene glycol and ethylene glycol are both used as antifreeze for cars and trucks They are chemically similar in many respects, with propylene glycol considered to be a safer alternative than its ethylene cousin; however, ethylene glycol has better heat transfer properties. Although propylene glycol antifreeze has less coolant ability and is less toxic than ethylene glycol, mixing them won't lessen toxicity or have a major effect on cooling ability.

Step 1

Place a 5 gallon bucket on level ground.

Step 2

Pour propylene glycol into the bucket, emptying only half of the 1 gallon container into it.

Step 3

Pour half the ethylene glycol into the bucket.

Step 4

Add in approximately 1 gallon of fresh water, using distilled water as an ideal choice.

Pour this 50/50 mixture into your radiator or automotive/truck overflow tank until full.


  • You can also pour each of them directly into your radiator or overflow tank, but trying to estimate a 50/50 water and antifreeze mix is a bit more difficult this way. No harm will come to your cooling system by mixing these two types of antifreeze together.


  • If pouring these glycols into your radiator directly, NEVER open the radiator or overflow tank when the engine is hot. Splashing and severe scalding may occur when opening a hot cooling system.

Items you will need

  • Ethylene glycol antifreeze in 1 gallon container
  • Propylene glycol antifreeze in 1 gallon container
  • 5 gallon bucket
  • Fresh water, distilled is preferred

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