How often should I change engine coolant

It’s easier to keep your cool than you might think, OK at least when we’re talking about our car’s cooling system.

Well, let’s start with the basics like “Why do you need to flush your radiator?” My answer might surprise you. You don’t. Are you a little surprised right now? Read on and I will explain why I say this.

Let’s start with the basic “cooling system”, what it is and what it does.

The cooling system is made up of the passages inside the engine block and heads, it uses a water pump to circulate the coolant, a thermostat to control the flow and thereby the temperature of the coolant, a radiator is used to cool the antifreeze, the system uses a radiator cap to control the pressure, and hoses to transfer the coolant from the engine to radiator (engine cooling) and “heater core” where hot coolant is used to heat the vehicle’s interior.

Here is a link to a good animation showing how this all works together, Cooling system operation

What you do need to do is to drain and refill the “antifreeze” or engine coolant as a part of regular “preventative maintenance”. Why? There are many reasons but let’s stick with two basics, system construction and chemical makeup of antifreeze.

System construction

Engine blocks will be constructed of either cast iron or aluminum, usually cast iron but this is changing as time goes by to more aluminum.

Cylinder Heads are now more often made of aluminum but some are still iron.

Same goes for water pumps, they will be made of aluminum or iron but also will have steel components in the pump shaft and impeller.

Radiators and heater cores used to be primarily copper and brass in construction but more often now are made of plastic and aluminum and in some instances will be all aluminum. Another point worth mentioning is that these newer radiators and heater cores now have much smaller passages now than their older counterparts. Read that as more prone to blockage.

Thermostats will usually be of either steel or stainless steel.

Hoses will be made of rubber or silicone.

What are the benefits of a “cooling system flush” – near 100% fluid exchange.

What are the risks? Damaged components.

One factor in the diminishing use of cooling system flushes is that today’s systems with aluminum radiators and heater cores can be damaged if the system is over pressurized by just a couple of pounds of pressure. Common operating pressures run between 14 to 16lbs.

For us, the risk of damaging a heater core that may require the removal of the dash to replace is just not worth the risk of using a flush machine. A drain and refill performed as a regular maintenance service is a better option that offers better protection for the cooling system as well.

This brings us to the chemical makeup of coolant. There are several different types of antifreeze depending on year make and model.

1. Automotive antifreeze has traditionally been made with ethylene glycol and Inorganic Acid Technology (IAT) corrosion inhibitors since 1926.

2. American vehicles have traditionally been designed to use antifreeze with silicates and phosphates as corrosion inhibitors.

3. European vehicles have traditionally used antifreeze that does not use phosphates.

4. Japanese vehicles have traditionally used antifreeze that does not use silicates.

5. Newer corrosion inhibitor technology includes Organic Acid Technology (OAT) and Hybrid Organic Acid Technology (HOAT). Both may be referred to as “extended life” antifreeze and were introduced in the 1990′s.

6. IAT antifreeze has a 2 year or 30,000 mile service life, where OAT and HOAT have a 5 year or 150,000 mile service life.

7. OAT based antifreeze is not compatible with IAT antifreeze; although, some HOAT formulas claim compatibility with certain OAT formulas or IAT formulas.

8. OAT and HOAT antifreeze is designed for use in aluminum radiators and components.

9. they Antifreeze is dyed to whatever color the manufacturer chooses and may help to distinguish the type of antifreeze (IAT, OAT or HOAT) or may be used to market variations of antifreeze formulas within a brand.

Overwhelmed yet?

In short, to tie this together, bi-metallic engines and associated components need the coolant to protect from corrosion and rust, lubricate the water pump, aid in heat transfer, prevent scale and protect from cavitation.

So the question changes to “how often should I change engine coolant”?

Depending on the year, make and model the manufactures recommend anything from 30,000 to 150,000 miles.

Cars.com stated;

Many service facilities, including some at dealerships that sell cars with “lifetime” Antifreeze, suggest you should do it more often than the maintenance schedule recommends, such as every 30,000 or 50,000 miles.

Modern vehicles have longer intervals between fluid changes of all types partly because environmental regulators have pressured automakers to reduce the amount of waste fluids that have to be disposed of or recycled.

Coolant can deteriorate over time and should be tested to see if it’s still good, as it can be hard to tell just by appearances. Even if testing shows the cooling and antifreeze protection are still adequate, antifreeze can become more acidic over time and lose its rust-inhibiting properties, causing corrosion.

Corrosion can damage the radiator, water pump, thermostat and other parts of the cooling system, so the coolant in a vehicle with more than about 50,000 miles should be tested periodically. That’s to look for signs of rust and to make sure it has sufficient cooling and boiling protection, even if the cooling system seems to be working properly. It can be checked with test strips that measure acidity, and with a hydrometer that measures freezing and boiling protection.

If the corrosion inhibitors have deteriorated, the coolant should be changed. The cooling system might also need to be flushed to remove contaminants no matter what the maintenance schedule calls for or how many miles are on the odometer. On the other hand, if testing shows the coolant is still doing its job and not allowing corrosion, changing it more often than what the manufacturer recommends could be a waste of money.

Here at London’s Automotive, Inc. we lean to the 30,000 to 50,000 mile range for most vehicles but like to test the coolant before we just replace it. After all, the goal is to ensure that your car or truck lasts as long as possible, in the safest manner, for the lowest cost reasonable, Right?

Don’t Lose Your Cool!