Originally posted by Big Jim:
Propelene glycol is the stuff that some alternative anti freeze companies (such as Sierra) have been pushing claiming that it is more environmentally friendly. Claiming that it breaks down more quickly when released into the environment and is not as toxic.
Ethylene glycol is toxic and when left loose often poisons dogs and cats. Propylene glycol, on the other hand, is so nontoxic that it can be legally used as a food ingredient. The performance differences are small enough that I am baffled why most antifreeze sold is not propylene glycol. You only need ethylene glycol if you live someplace that gets like 50 degrees below zero.
Sierra is not an alternative company, by the way, it's just a brand used by one of the regular antifreeze companies for their propylene version.
