First, I'm not
talking about potable water systems
. PG is much less toxic to mammals than EG
. That is well established, so let us skip that discussion. Black water and engine systems only.
Let's avoid cost discussions. They are in fact very, very close, with EG generally cheaper. PG antifreeze typically apears cheaper because the -50 burst stuff only contains 25% PG.
Why does it matter?
* I've been doing some immersion testing of marine parts in PG and EG and the results for PG are not pretty. Neoprene gets hard. Nylon crazes.
* I have spoken with a number of respected marine mechanics who unanimously agree that PG ruins neoprene water pump impellers.
* These problems are also well known in the automotive engine coolant industry, perhaps the secondary reason all OEMs avoid using PG (primary is that is an inferior heat transfer and antifreeze agent).
So I did a little reseach that I posted here:
Sail Delmarva: EG vs PG: Conventional Wisdom That is Provably Wrong
In a nutshell, I could find no credible data that sugested any important difference.
From Risk World (European conference)
"Based upon the limited available data, no general distinction can be made between aquatic toxicities of ethylene and propylene glycol formulations."
I have also contacted a number of environmental agencies and groups that post PG recomendations on-line. Of course, none had done any research of their own. Their answers are variations on:
* We got our information from (another site with no data).
* "Everyone knows...."
* Liability concerns. Someone will use EG in the potable system.
* "We are concerned about heavy metals" (While there are heavy metals in used vehical engine coolant, that is not a EG/PG difference).
Does anyone have data regarding EG/PG and marine toxicity that tells a different story? Is there some other reason?