Caution: These new long life coolants provide extended life only when used in a clean system mixed with water. If mixed with ordinary antifreeze and/or old coolant in a system, the corrosion protection is reduced to that of normal antifreeze (2 to 3 years and 30,000 miles).

Corrosion Inhibitors: The life of the antifreeze depends on it's ability to inhibit corrosion. Silicates, phosphates and/or borates are used as corrosion inhibitors to keep the solution alkaline. As long as the antifreeze remains so, corrosion is held in check and there's no need to change the coolant. But as the corrosion inhibiting chemicals are used up over time, electrolytic corrosion starts to eat away at the metal inside the engine and radiator. Aluminum is especially vulnerable to corrosion and can turn to Swiss cheese rather quickly when conditions are right. Solder bloom can also form in copper\brass radiators causing leaks and restrictions. So changing the coolant periodically as preventative maintenance is a good way to prevent costly repairs.

The basic idea is to change the coolant before the corrosion inhibitors reach dangerously low levels. Following the OEM change recommendations is usually good enough to keep corrosion in check, but it may not always be the case. That's why more frequent changes may be recommended to minimize the risk of corrosion in bimetal engines and aluminum radiators.

Checking the Antifreeze: One way to find out if it's time to change the antifreeze is to test it. Several suppliers make special antifreeze test strips that react to the pH (alkalinity) of the coolant and change color. If the test strip indicates a marginal or bad condition, the coolant should be changed.

Changing the coolant: Reverse flushing is the best way to change the coolant because draining alone can leave as much as 30 to 50% of the old coolant in the engine block. Reverse flushing also helps dislodge deposits and scale which can interfere with good heat transfer.

The concentration of antifreeze in the coolant also needs to be checked prior to the onset of cold weather. A 50/50 mixture of antifreeze and water is recommended. For maximum protection, up to a 70% mixture of antifreeze can be used.

Caution: Do not use more than 70% antifreeze, and never run straight water in the cooling system because it offers no corrosion, freezing or boilover protection.

Answer: It's propylene glycol (PG) antifreeze. Every other brand of antifreeze contains ethylene glycol (EG). Antifreeze made with propylene glycol is being marketed as a "safer" alternative to ordinary antifreeze. Though it is by no means safe to drink, it is significantly less toxic than ordinary ethylene glycol antifreeze -- which may be a important difference to pet owners and parents of small children. PG also has an unpleasant taste which discourages further sampling by thirsty animals and toddlers. Safety is an important issue with coolants because of the frequency of spills, leaks and improper disposal.

Because of its significant safety advantages, PG coolants represent far less risk to wildlife in case of spills, leaks, or careless disposal. Because of this it can be claimed that PG coolants have an environmental benefit. However, both PG and EG are biodegradable and both may pick up lead or other heavy metals once they've been used in a cooling system. Both types of coolants, after being used, should be disposed of properly and in compliance with local regulations.

Though some auto makers were initially cautious about using PG when it was first introduced, GM has now said that propylene glycol may be used in GM vehicles without voiding the manufacturer's warranty coverage and will perform adequately under most vehicle operating conditions. Most vehicle manufacturers, however, don't currently use PG as a factory-fill antifreeze because of its higher cost.

Antifreeze Disposal & Recycling: Regardless of the type of antifreeze you use, it should be disposed of properly. It is okay to flush used coolant down the toilet (sanitary sewer) as long as the amount does not exceed a few gallons. But it should not be poured down a floor drain or into a storm sewer. Both types of antifreeze are biodegradable but take some time to break down. Dumping used antifreeze into a storm sewer, ditch, creek or on the ground can contaminate ground water and kill plants and fish. What's more, used antifreeze picks up lead from solder in copper/brass radiators. Lead is a toxic heavy metal that can also cause pollution problems of its own. You can also take your vehicle to a garage or service facility that has a coolant recycling machine. The latter is the best choice because it eliminates the disposal problem altogether. Coolant recycling machines work their magic by a variety of means. Some use filtration while others use a distillation process to remove the harmful contaminants from the old antifreeze. Corrosion inhibiting chemicals are then added to restore the coolant's corrosion protection. The auto makers have all approved coolant recycling as an effective means of eliminating coolant disposal problems, and each publishes a list of machines that meet their specifications. Recycled coolant must meet minimum standards of purity before it can be reused.