Winter Coolant

You might think antifreeze isn’t an issue in San Diego.  That would be true if all it did was protect against freezing.  But it does a lot more, and is just as important in protecting your vehicle as motor oil.  So there’s no reason to neglect the coolant system in the winter.

Antifreeze? Coolant? Protectant?

These terms are often used interchangeably, since one product serves all three functions.

Cars and trucks still need a well-working cooling system year-round to get rid of the huge amount of heat that the engine generates.  But if that coolant should freeze while the vehicle is parked it expands and can do serious damage.  To the point of leading to a radiator repair or even damaging the engine block.

So water simply isn’t enough.  Coolant has a lower freezing point and a higher boiling point so it protects against freezing and greatly reduces the odds of boil over while helping to maintain the right engine operating temperature.

It also contains additives to protect just about every part of the cooling system.  They inhibit rust and corrosion, reduce scale build-up, protect seals, and lubricate water pump bearings. But those additives break down over time, and the coolant eventually needs replacing.

Coolant By the Numbers

For decades, the major ingredient in antifreeze/coolant has been ethylene glycol. Surprisingly, a mixture of glycol and water has a lower freezing point than either alone!  It also raises the boiling point by about 20 oF, although pound per pound it transfers about 65% as much heat as water.  Unfortunately antifreeze happens to be both sweet-tasting and toxic, so it’s a danger to bets and children.  That’s why many products have switched to propylene glycol.  It’s a bit more expensive but performs almost identically,

In areas with mild winters it’s common to use a mixture of 60% water and 40% glycol.  But in San Diego it’s more common to keep it simple with a 50%-50% mixture for extra protection.  You never know when you might head out for skiing or a road trip!

Why use a mixture at all?

100% water offers no protection at all and 100% glycol just doesn’t have enough heat capacity.  And remember glycol alone has a higher freezing point.

Most people simply buy pre-mixed coolant.  If not, never use plain tap water.  Or add plain tap water to your radiator.  That’s likely to lead to scaling and in turn poor engine cooling.  And possibly even damage.  Use only distilled water.


Glycol Water Freezes At Boils At *
50% 50% -34 oF 265 oF
70% 30% -84 oF 275 oF


* In pressurized cooling system.

Be Prepared

Here’s some maintenance tips.

It’s a good idea to check your cooling system yourself from time to time.  With the engine cold (otherwise you could be hit with high-pressure steam!), remove the radiator cap and have a look.  Is the level up near the top?  Is the coolant bright and colorful, or brown and muddy.  If it’s the latter it’s time to get rid of that old coolant.  Check that the seal on the radiator cap is in good condition.  Are all the hoses in good condition?  Also check the level in the reservoir.

Since you usually need an oil change around twice a year, it’s a good idea to have seasonal maintenance on your coolant system in the fall and spring as well.  Depending on your vehicle and the exact type of coolant used that should include a coolant flush anywhere from every 30,000 to 150,000 miles (every few years).

Don’t Take Our Word for It

A survey by reported that 27% of cars checked had low coolant levels and 20% needed a flush.  That’s a big risk for winter driving!

Visit Pacific Auto for Coolant and All Other Vehicle Maintenance

Our ASE certified technicians and master mechanics work with the latest diagnostic equipment.  And we guarantee all our work.  Give us a call or stop by!