Car radiator coolant is a mix of anti-freeze and water. Engine coolant is designed to protect your car radiator and cooling system all year round. Many different brands and varieties of engine coolant exist. Most have additives that are intended to protect your cooling system by preventing corrosion, lubricating, and increasing cooling efficiently.

1. Ethylene Glycol/Polyethylene Glycol. Tried and true, this type of anti-freeze is still standard after almost 70 years. Modern ethylene glycol anti-freezes have several additives to protect, clean, and lubricate your cooling system.

2. Non-Toxic Radiator Coolant. This anti-freeze does not contain ethylene glycol or polyethylene glycol (both acutely toxic). These engine coolants are, however, still toxic but only in larger quantities and over longer periods.

3. Extended-Life Anti-Freeze. In most cases, this is simply an ethylene glycol anti-freeze with one or more carboxylate additives to prevent corrosion of the cooling system. These engine coolants should make your car radiator and cooling system last longer.

Engine Coolant Additives
Engine coolant additives for your car radiator are meant to:

	Reduce cooling system corrosion. Every cooling system will corrode eventually, but you might as well slow the process down as much as you can.
	Reduce cavitation. In large diesel engines, air or tiny bubbles in your coolant can cause serious problems. If you own a diesel vehicle, it is highly recommended that you use a cavitation reducing engine coolant.
	Buffer the acidity of your engine coolant. The more acidic your engine coolant, the more quickly it can corrode and damage your cooling system and car radiator.
	Raise the boiling point of the engine coolant. A higher boiling temperature means that the coolant can cool better as your engine gets hotter. It also reduces the chance of blowing a head gasket.

Common engine coolant additives include: nitrates (corrosion inhibitors, buffers), silicates (corrosion inhibitors, especially for aluminum radiators), carboxylates (buffers, corrosion inhibitors), and borates (buffers). Never mix different types of engine coolant. You can damage or further reduce your car radiator’s efficiency by mixing the different types. Before you change types, thoroughly drain and flush your cooling system.