glycol confusion

Okay, now I'm confused.

I'm about to refill my 328's cooling system after replacing a split hose that bathed my driveway in antifreeze. After having to flood the drive before the local critters got to the ejected antifreeze, I picked up some "pet friendly" antifreeze at the auto parts store.

But I thought I'd check to see if it's compatible with the car first.

I didn't find much information here, so I went with a wider google search, including ethylene glycol (EG) (common antifreeze), propylene glycol (PG) ("pet friendly" antifreeze), and (for the heck of it) polyethylene glycol (PEG) (which I saw advertized as an over-the-counter laxative). (Would something safe for OTC human consumption be a good antifreeze? )

Now I'm really confused.

I've seen both EG and PEG listed as "toxic antifreeze". I've seen serious warnings about skin exposure to PG, .... but PG is a component of many skin care products. Apparently CDC deems PG safe as a food additive, but FDA rejects cat food containing PG as unsafe.

Now I've seen all the threads about Water Wetter and using plain water in the cooling systems. But I want something for year-round use where it gets cold.

But it sounds like the variations on glycol are both very different and much alike at the same time.

All I really get about the various glycols on the internet is that confusion is par for the course.

Can any organic chemists shed some light on this subject?

Or at least is it okay to use propylene glycol ("pet friendly") antifreeze in a 328? (Safe for the car, at least?)

 

I did a bit more research on the PG/EG issue. While the store display said "mixes with any antifreeze" (it may have been referring to the "extended life" in the same rack), the Prestone site talks about flushing the system before refilling with PG.

PG takes a different hygrometer than EG, to test the concentration, and a mix requires a refractometer to figure out what protection you have. Since refractometers run around $100 (compared to the $5 special EG hygrometer), I decided not to add PG to the remaining EG.

For the sake of bleeding the system, I added three gal of plain water. (So there was two gal of 50/50 EG left in the system.) It takes longer to warm up, but idles around the same temp as with 50/50 -- cycling with the fans.

I managed to get the air out (pressure bleed) -- which is surprising, as it used to take two or three tries. Maybe I'm getting the hang of it.

Eventually, I'll probably add EG by swapping out what's in the expansion tank. I probably want to raise the boiling point a bit over plain water.

By my math, it would be around 20/80 at this point. But it might have been a bit thicker than 50/50 to start with -- the coolent the car dropped a week ago on the floor lift rubber pad is still liquid. And the oil cooler began smoking -- as it cooks off the stuff spilled on it. I'm tempted to hose down the engine -- but I'm thinking that may not be a really good idea, given that the coils are in that same area.