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Coolant Recycling

by Larry Carley copyright

recycle antifreeze

Does your car need a coolant change? If so, you should consider having the old coolant recycled rather than replaced. Recycling is a way to reuse old coolant. It's a green technology that is good for the environment and good for your pocketbook.

Over time, the corrosion-inhibiting additives in antifreeze are gradually used up. After five years of service, even long life coolants need to be changed. If the coolant is not changed, it may no longer be able to prevent corrosion inside the cooling system, which could result in expensive damage.

For years, most vehicle manufacturers and aftermarket antifreeze suppliers have recommended changing ordinary green formula coolant every two years or 30,000 miles in passenger cars and light trucks. With long life coolants, the recommended replacement interval is five years or 150,000 miles, which ever comes first (not last!).


When a change is due, the old coolant can either be dumped or recycled. Recycling is the environmentally friendly alternative because it keeps ethylene glycol and all the nasty stuff it picks up inside the cooling system out of the environment.

Yet, of the more than 180 million gallons of antifreeze that are sold each year in the U.S., less than 15% is currently being recycled! Ethylene glycol, which is the main ingredient in most antifreeze, almost never wears out. In the open air, it will slowly evaporate and can oxidize breaking down into water and carbon dioxide. But when mixed with water and sealed inside an air-tight cooling system, it can almost last forever.

What does not last forever is the corrosion-inhibiting additive package in the antifreeze. Nor does the coolant remain clean forever. When the additives become depleted, the coolant either needs to be replaced or replenished.

Adding a dose of chemicals to the radiator may help extend the coolant's corrosion resistance, but it won't remove all the impurities that have accumulated over the years. The coolant picks up a lot of junk from inside the cooling system as well as from make-up water that may be added to the radiator.

Though vehicle manufacturers all recommend using deionized or distilled water in a cooling system, most people use ordinary tap water. This is bad news for the coolant because ordinary water contains a lot of minerals.

Minerals form scale and react with the additives in the coolant to reduce their effectiveness. Softened water is even worse because it contains chlorides (from sodium chloride), and, as we all know, salt equals corrosion. As rust and corrosion eat away at the metal, debris enters the coolant causing it to discolor. The debris can damage the water pump seal, cause thermostats to stick and clog radiator and heater tubes. The only way to get rid of the contaminants is to replace the coolant with either new coolant or coolant that has been recycled using an OEM-approved method.

The coolant also picks up lead from soldered joints and seams in copper/brass radiators on older vehicles. Though most late model cars and trucks have aluminum radiators (over 90% of new vehicles, and about 60% of all vehicles that are on the road), there are still a lot of older vehicles that have copper/brass radiators and heater cores. Newer applications use lower lead content solder, but older vehicles as well as some aftermarket replacement radiators still use solder that is 92% to 98% lead. Lead does the cooling system no harm, but it creates a potential disposal problem. Lead is one of the heavy, toxic metals that we do not want in the environment. So even if your local water treatment facility allows used antifreeze to be dumped down your sanitary sewer drain, the lead will still end up in the environment.

Speaking of dumping, the worst thing anybody can do is dump used coolant down a storm sewer or onto open ground. Ethylene glycol is poisonous to humans, animals and plants. Though it will eventually break down, it can do a lot of environmental damage in the meantime especially if it seeps into ground water. A single gallon of used antifreeze can make 10,000 gallons of ground water unsafe to drink!

The U.S. Environmental Protection Agency does not consider used antifreeze to be a hazardous waste - provided it does not contain more than 5.0 parts per million of lead. The waste generator (your shop) is responsible for having the lead content of the coolant tested before it is disposed. Unless you have some way of separating used coolant from vehicles with copper/brass radiators from those with aluminum radiators, there is no way to know how much lead might be in a 55-gallon drum full of used antifreeze. Testing is the only way to know for sure. Yet many people do not. Some do not even worry about such regulations and take their chances when it comes to dumping their used antifreeze. Others try to abide by the rules and end up paying high fees to licensed hazardous waste haulers (which can cost from as little as 50 cents a gallon to $1.50 or more for antifreeze).

Recycling antifreeze solves the environmental issue by keeping lead and other contaminants out of drains and sewers. It also allows a valuable resource to be reused almost indefinitely. Ethylene glycol is made from natural gas, which is in no short supply for now. But producing it consumes energy. Recycling is more energy-efficient and lessens the demand for virgin antifreeze - which helps keep the overall price of antifreeze down.


A typical jug of antifreeze contains 95% ethylene glycol (EG) by weight, 2% corrosion inhibitors (silicates, phosphates and/or borates) and 3% water (a little water is added to help blend the inhibitors with the glycol). The proportions are about the same for propylene glycol (PG) antifreeze, but PG is only used in a few applications as original equipment (Audi and VW), though it is readily available in the aftermarket as a "safer" (less toxic) alternative to ordinary antifreeze.

Ethylene (or propylene) glycol is the part of the coolant that is recycled. Coolant should normally contain about 50% antifreeze by volume, but depending on how much make-up water and/or antifreeze have been added over a period of time, the mix could be almost anything. But it really doesn't matter because the coolant from a number of vehicles is combined before being treated to remove impurities and restore the additives.


When a repair facility recycles your old coolant, they will usually filter it, clean it using one of several methods, and add the proper chemicals to restore the corrosion inhibitors so it will perform like new.

Most of the professional coolant recycling machines use some type of filtration process and chemical reaction to remove contaminants from the coolant. The coolant is pumped though a filter (sometimes more than once), and additional chemicals (flocculants) may be added to precipitate out other impurities such as emulsified oils and heavy metals. After filtering, an additive package and dye is added to restore the corrosion inhibitors of the antifreeze. The effectiveness of the cleaning process can vary from one manufacturer's equipment to another, as can the quality of the additives that are used (some meet OEM specs, others do not).

The additive package can be an issue depending on the application. The additives used in North American and Asian coolants usually differ from those used by European manufacturers. The Europeans usually specify an additive package that contains no phosphates and uses borates and low silicates. Their reason for doing so is because Europe has hard water which can react with phosphates to form calcium and magnesium sediments. Asian vehicle manufacturers, on the other hand, typically use phosphates but no borates and low or no silicates. They do not want borates in the system because they believe borates can corrode aluminum if the coolant is neglected for too long.

Using an antifreeze that does not meet the OEM requirements may void the vehicle manufacturer's warranty. Even so, filling European or Asian cooling systems with a typical North American additive package (which contains silicates, phosphates and borates) should cause no problems. And once a vehicle is out of warranty, it should make no difference what type of antifreeze is used in the cooling system as long as it provides adequate corrosion protection.

Large off-site recyclers use a more sophisticated process, either reverse osmosis or distillation to separate out the ethylene or propylene glycol from the water and contaminants. These two processes are the only ones that can remove chloride salts from the solution, and deliver a virgin glycol product. But such a high level or purity really is not necessary say those who market equipment that have OEM approval for repair shops.

A group called the American Society of Testing Materials (ASTM) has developed coolant recycling standards that assure a certain level of quality. Critics say the standards are too stringent on chloride levels, requiring less than 33 parts per million in recycled predilute antifreeze (new antifreeze must contain less than 25 ppm chlorides to meet ASTM standards). The only recycling processes that meets such standards are reverse osmosis and distillation - both of which are too expensive for small in-shop recycling applications.


In 1996, General Motors began factory filling all their cars and light trucks with "Dex-Cool" antifreeze. Dex-Cool is made by Texaco and is marketed under the Havoline "Extended Life" brand name.

Dex-Cool has a service life of five years or 150,000 miles, and is dyed orange so it can be easily distinguished from ordinary green antifreeze. It is an ethylene glycol antifreeze but contains a unique corrosion-inhibiting chemistry that uses an organic acid technology (OAT) additive package instead of silicates, phosphates or borates.

GM says Dex-Cool should NOT be intermixed with ordinary antifreeze because doing so reduces the service life of the new coolant to that of ordinary coolant. Many motorists do not know this and may add ordinary coolant to top off their cooling system. In so doing, they reduce the service life of their coolant by half or more.

Ford also uses an OAT-based silicated hybrid antifreeze in their 1999 Mercury Cougars, and Chrysler uses a silicated OAT orange antifreeze in 1998 and 1999 LH models (Dodge Intrepid, Chrysler Concorde, Chrysler 300M).

As long-lived as OAT-based antifreezes are, GM does not recommend using Dex-Cool in older vehicles with copper/brass radiators and high lead solder seams. The reason is because the additives in Dex-Cool can eat away at the solder leading to premature radiator failure. There is also concern that it can erode water pump impellers that experience lot of cavitation (new GM engines have specially designed water pump impellers to minimize cavitation).

Dex-Cool has experienced some problems in GM applications at relatively low mileages. If the coolant level is low, or the concentration of antifreeze in the coolant drops too low (say 25% instead of the normal 50%), sludge deposits can form that plug up radiators, heater cores and cooling jackets. Some problem applications have included the cast iron 4.3L V6 engine in Chevy/GMC S-10 pickups and Blazers/Jimmys (these vehicles do not have a pressurized coolant reservoir).

The plugging problem has created a demand for "retrofitting" new GM vehicles back to ordinary antifreeze. Though GM does not approve this, people who have experienced problems with Dex-Cool (or who want to avoid the risk of such problems) are having Dex-Cool removed and replaced with conventional antifreeze.

What about recycling Dex-Cool? Some say it is better to dispose of the stuff when servicing a vehicle and refill with ordinary coolant. But several coolant recyclers we interviewed for this article said their machines could recycle Dex-Cool - but they recycle it into ordinary antifreeze with a conventional silicate additive package.

coolant recycling More Cooling System Articles:

Finding & Fixing Coolant Leaks

Servicing Your Cooling System

Radiator Repair & Replacement

Your Temperature Warning Lamp Is On. What Should You Do?

Overheating: Causes & Cures

Coolant Sensors

Water Pump Diagnosis & Replacement

Troubleshooting Cooling Problems with Temperature

Coolant Checks & Changes More Complicated These Days

Coolant Types

Universal Coolant: One Antifreeze For All?

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