Recycling Antifreeze

[UncleWillie]

A few people on here have mentioned in passing that they recycled their Antifreeze.

I tried an experiment last year...

Drain the block.
Run RV (Propylene Glycol, PG) Antifreeze through the system.
And then drain it again!
Yes, Air doesn't Freeze, I know!

I place a cheap child's/infant swimming pool under the out-drive to catch all the drips and drains.
Pour the Antifreeze through a cloth to filter out the debris and stored it in a five gallon pail.
After a couple of weeks in a heated garage with the lid Off, the excess water in the mix evaporates leaving 3 to 4 gallons of full strength PG.
Water evaporates; PG not so much.
It feels similar to baby oil at this concentration.

A test comparing brand new PG, Rated at -50F, with the recycled PG in a freezer showed the brand new PG was slushy at -5F and the recycled stuff was still fully liquid.
Note: -50F rated PG is expected to become slushy Below +16F.

This is not a case of spending a few hour trying to save a few bucks.
It is a case of saving a few buck, and spending a few hour trying to save the environment.

Instead of dumping the Antifreeze, recycle it!
I doesn't go bad. After evaporating off the water, put a lid on the pail until next year.
The recycled -50F grade PG is concentrated into full strength -100F PG for very little effort.
And next year you'll only need to buy 1 or 2 gallons instead of 5 or 6!

 

[90stingray]

Re: Recycling Antifreeze

RV/marine antifreeze is biodegradable. I have no problem letting the pink stuff get diluted with the fresh water during spring start up and go right down the drain. It says its safe for aquatic life... so i imagine having an engine block full and going straight to the lake in the spring is acceptable too. Now if its the real deal antifreeze... like the green or orange... thats another story. And i dont know why someone would use that stuff in a boat anyways.

http://www.splashwash.com/Product.aspx?pid=7

 

[Ned L]

Re: Recycling Antifreeze

Good info, Thanks! I have a couple of gallons that I used last winter & had been wondering about using it over again. -- I run it though the engine & then drain the block when I pull the engine out of the boat for the winter (yea, I do.... pull the engine)

 

[DBreskin]

Re: Recycling Antifreeze

I doesn't go bad. After evaporating off the water, put a lid on the pail until next year.

If it's biodegradable, maybe it does go bad. You need to try the freezer test again after the antifreeze has been stored for a year.

 

[UncleWillie]

Re: Recycling Antifreeze

I knew there were more people that were secretly recycling.

Evaporating the water increases the concentration of the Propylene Glycol (PG).
PG's evaporation rate is many time slower than water.
If you are really nerdy, (I confess!), a small aquarium heater in the pail will speed up the process.
If you leave the container open long enough, all the PG will eventually evaporate.

I found the freezer test to be the easiest to see how good the antifreeze is.
If your recycled stuff in a small plastic bottle has less slush in it than a sample of brand new PG, You're Good!

For the OCD types, (I confess again!) for a couple of bucks at any saltwater aquarium store, you can get a Hydrometer to measure the strength. Anything over 1.040 is better than new! 1.050 is full strength.

For the environment it is "Generally Regarded As Safe" (GRAS).
Meaning it doesn't do a lot of harm in small quantities.
You can drink a small glass of it and it won't kill you.
Tastes like Nyquil! But, may exit your system within the hour!

It does biodegrade with oxygen; Meaning it will deplete the oxygen in the water for the fish.
It turns into water and CO2 eventually.
The algae in the water will appreciate it by growing faster.
Is it a major noticeable issue. Not hardly! But it is there.

 

[UncleWillie]

Re: Recycling Antifreeze

If it's biodegradable, maybe it does go bad. You need to try the freezer test again after the antifreeze has been stored for a year.

The lid on the pail should prevent any more oxygen getting to the liquid.

Retesting is always a good idea.

 

[tpenfield]

Re: Recycling Antifreeze

Perhaps a reason to recycle the AF is for cost considerations . . .

. . . I looked at the AF in West Marine ($4.99/gal). . . then bought the AF at Walmart ($2.96/gal)

I am feeling less of a need to recycle.

 

[UncleWillie]

Re: Recycling Antifreeze

Perhaps a reason to recycle the AF is for cost considerations . . .

. . . I looked at the AF in West Marine ($4.99/gal). . . then bought the AF at Walmart ($2.96/gal)
I am feeling less of a need to recycle.

Saving money is not the primary consideration for recycling.

Be cautious with the "Too good to be True" AF from Walmart.
I almost bought some until I checked the label closely.
The super low priced stuff was Alcohol based, Not P-Glycol.

 

[matt167]

Re: Recycling Antifreeze

Yes, some of the pink RV antifreeze is basically blue washer fluid with pink dye instead. Some has a stronger concentration of alchahol than the blue stuff and is popular for methanol injection for cooling forced induction engines.

 

[Chris1956]

Re: Recycling Antifreeze

Willie, I disagree with you on several points. First of all, after fogging and draining the block, fill it with full strength antifreeze, and leave it in over winter. What is the point of draining it at that time?

Secondly, in the spring drain it into the orig containers and store it over the summer. Reuse next year, supplementing with new as needed.

Thirdly, Automotive antifreeze has antirust and seal lubricating properties. I do not think RV antifreeze has those, and I like those properties for my cast iron block. and water pump.

Although, I have never worked with RV Antifreeze, I have a hard time believing that water will evaporate out of the AF-water mix, leaving the pure A-F behind. Once water mixes with the A-F, they appear to be inseperable, and share a common freezing and boiling point.

 

[cooleyo]

Re: Recycling Antifreeze

"Although, I have never worked with RV Antifreeze, I have a hard time believing that water will evaporate out of the AF-water mix, leaving the pure A-F behind. Once water mixes with the A-F, they appear to be inseperable, and share a common freezing and boiling point. "

^^Not true. In school we used to run a glycol/water unit to help learn basics of distilling. Boiling point of Propylene glycol is 370.8? F (188.2? C). Also, whats the point of using ANTIfreeze, if it freezes just like water?

 

[90stingray]

Re: Recycling Antifreeze

Thirdly, Automotive antifreeze has antirust and seal lubricating properties. I do not think RV antifreeze has those.

The rv plus brand that i bought says it is a superior corrosion inhibitor.

 

[Brewman61]

Re: Recycling Antifreeze

Distilling is one thing, evaporation may be another. And Antifreeze doesn't freeze like water.
Propelyne Glycol doesn't expand when it freezes. I've had bottles of the stuff go slushy on me in the
coldest part of winter, like -30F or colder , it doesn't expand and burst the container like water would.
PG is also a very common food additive, and it's non toxic and environmentally friendly, which is why
it's used to protect potable water systems in campers over the winter. Ethelyne Glycol, the common stuff
in automobile cooling systems is deadly poisionous and should not be dumped into the water.

 

[UncleWillie]

Re: Recycling Antifreeze

Many good points guys!

I did a lot of research on this before I suggested the method.

The water will truly evaporate out of the PG mix.
I have tried a half dozen ways to Evaporate/Distill it.
It does not like to be cold, the warmer the better.
I tried it in an unheated detached garage (50F) and saw almost no improvement.
It doesn't work very well below 70F. It takes Energy/Heat to evaporate water.
Heated to 85F and it evaporated almost a quart a day.

Propylene Glycol (PG) is essentially a Bio-friendly water soluble oil.
While doing your winterizing this year; Stick your finger in the antifreeze and taste it!
It won't kill you! It tastes like Cough Syrup because it is a major ingredient in Cough Syrups.
A teaspoon every few hours is benign; You would have to chug a pint of 100% PG to get into trouble.
Small children drinking the whole bottle of Cough Syrup can become ill but are treatable and survive.

PG is GRAS (Generally Regarded As Safe) by the FDA. But it is not like drinking sugar water by any means.
It doesn't destroy the enviroment on contact, but it is not doing it any good either.
I would not characterize it as "Enviromentally Friendly" as much as "Enviromentally Tolerable."


The Anti Rust/Corrosion Inhibiting and lubrication properties are Marketing Statement.

PG is a water soluble Oil. Pour some on your hands. It feels Oily. Oil Lubricates!
All PG made by any of the manufacturers does the same thing. Marketing!

PG naturally absorbs oxygen in it's biodegrading process.
This will deplete all the oxygen in the interior of the engine.
All PG made by any of the manufacturers does the same.
No Oxygen, No Rusting! Corrosion Inhibitor! Marketing!

A glass of -50F PG in your Kitchen freezer WILL turn to slush.
It is firm enough to turn the glass upside down and not a drop will come out.
It is not firm enough to break the glass. You CAN Stick a Fork in it! Try it!
The -50F Rating on the bottle is the temperature it protects from BURSTING Not Freezing!

I am not asking you to believe me just because I say so. Go try it yourself!
These are easy inexpensive experiments to do. And very Interesting and Fun too!
Don't just make blind statements that it doesn't work. Prove me wrong!

 

[Chris1956]

Re: Recycling Antifreeze

OK, Wikipedia is a facinating place. Mixing 30% water with Ethylene Glycol lowers the freezing point of the EG from 9*F to -60*F. Makes for a real good antifreeze solution. A 30% water solution has a boiling point of 240*F. Again plenty of boilover protection for an automobile.

Interestingly enough, mixing water with propyolene glycol raises the freezing point of the PG. That begs the question of why mix any water with the PG, when using it as a coolant? There was no information on the boiling point. There was no thermal conductivity properties specified for EG, so I have no way to judge the effectiveness of the PG in removing heat.

Interestingly enough if you look up Antifreeze on Wikipedia, it will tell you the shortcomings of both EG and PG. Looks like EG is a better Antifreeze, if the toxicity is not an issue.

 

[tpenfield]

Re: Recycling Antifreeze

Saving money is not the primary consideration for recycling.

Be cautious with the "Too good to be True" AF from Walmart.
I almost bought some until I checked the label closely.
The super low priced stuff was Alcohol based, Not P-Glycol.

Yes, so I did check the label, etc on the "Super Tech" brand from Walmart and compared it to some of the higher priced stuff that I have on hand.

The cheaper stuff has a combination of PG and alcohol. The "Seafit" brand from West Marine has just PG at a 30% blend. The published specs are substantially the same, and what is interesting is that 'slushing' occurs around 0 degrees F with both products (the -50 F formulas), and both products recommend using the "-100 F" formula if there will be temperatures below -10 F.

So, if you are in 'cold country' probably should be using the -100 F stuff.

 

[gddavid]

Re: Recycling Antifreeze

Interestingly enough, mixing water with propyolene glycol raises the freezing point of the PG. That begs the question of why mix any water with the PG, when using it as a coolant? There was no information on the boiling point. There was no thermal conductivity properties specified for EG, so I have no way to judge the effectiveness of the PG in removing heat.

Water has a higher specific heat than EG so it has more capacity to carry heat to a radiator than EG does. Good question. Salt water also has both a higher boiling point, lower freezing point and greater specific heat than fresh water but we it isn't the preferred coolant for other obvious reasons.

 

[UncleWillie]

Re: Recycling Antifreeze

Interestingly enough, mixing water with propylene glycol raises the freezing point of the PG. That begs the question of why mix any water with the PG, when using it as a Coolant? There was no information on the boiling point. There was no thermal conductivity properties specified for EG, so I have no way to judge the effectiveness of the PG in removing heat.

Interestingly enough if you look up Antifreeze on Wikipedia, it will tell you the shortcomings of both EG and PG. Looks like EG is a better Antifreeze, if the toxicity is not an issue.

PG and EG properties can be found HERE.

EG is a better antifreeze than PG in some situations, however the advantage is slight.
EG's biggest selling feature is it's cost. It is just less expensive to produce than PG.

PG is seldom used for COOLING except in cases where toxicity is an issue.
100% PG has freeze protection down to -200F. Way overkill for most situations.
The primary reason for adding water is to save money.
One gallon of 100% PG can be diluted to make 3 gallons of -50F Antifreeze or 2 Gallons of -100F
Most areas of the US seldom get below -20F.
Buying -100F may give you that warm fuzzy feeling but really gives no more real protection.