Anti freeze v. water


I have an audi A4 with 200k miles. I live in a moderate climate. What happens if instaed of anti freeze, I fill it with water?


The boiling point of water is less than that of an anti-freeze/water mix, so the water becomes steam, and steam does not cool the engine like water does. It’s a bad idea. Also, water doesn’t add lubrication for the water pump or anything to slow down corrosion.


You should not be using either on their own, but a ~50/50 mix of the two. Water freezes too high and boills too low, straite antifreeze is not good at all. That 50/50 can be off by some though, if you are a little low you can top it off with water.


Surf’s Up, Dude!

Water should work just right!
Be sure to line the entire interior with plastic sheeting first. A good 4 or 6 mil plastic available at the hardware store should do it. Seal the seams with a silicone sealant. Fill only to bottom of windows. You will have to enter and exit through the window openings. Allow extra stopping distance due to possible sloshing and added weight.

Good Luck!


Water doesn’t have the rust inhibitors that you find in coolant/antifreeze. So expect your radiator and heater to rust out. But before that happens, the water will turn brown and rust chunks will clog up the fins in the radiator and heater core.

I live in a moderate climate too (Noetheast Florida). It freezes here about twice a year. When I lived in Miami, it would get down to freezing temperatures about once every five years. So even if you live in a moderate climate, you still want antifreeze in your car for those rare freezes. Besides, in hot weather, water doesn’t offer the same protection as coolant.



Besides Antifreeze lowering the freezing point of a 50/50 mixture to about -35…it also raises the boiling point to about +260. You’re car will NOT run right if the water temp gets too high.


the term “anti freeze” has you grossly mis-led. COOLANT is anti-freeze AND anti-boil AND corrosion protection AND lubricant. Don’t EVER use water only in your automotive coolant system.


Years ago Antifreeze was just Alcohol. It prevented the water from freezing. Problem was you didn’t want to use this during the summer.

The stuff that we’ve been using for the past 40+ years not only lowers the freezing point of water…but raises the boiling point…and as ken pointed out…has the corrosion protection and lubricant…The last two are very important for the longevity of your cooling system.

50/50 mixture is the best mix. Lowers the freezing point to -35. Not too many places in the country ever get below -35. Coldest day I ever saw was -26.


What do you have to test the “strength” of your coolant?

As a professional I bought a tool that you put a drop of the coolant on a “window” then looked through a lens and you could see a scale and a line that told you to what temp you were safe. I believe these “prisim’s” are more common in Europe,but I bought mine here.




I would only do it in an emergency if I could not get antifreeze.


Your water pump will leak or your engine will overheat or your cooling system will plug from corrosion. Be thrifty and use anti-freeze per instructions.


Plus, you need extra corrosion protection for the aluminum in the engine. Straight water will corrode through aluminum a helluvalot faster that older cars with cast iron engines.


Water has a higher specific heat (absorbs more heat per degree temperature rise) than an antifreeze/water mix, so in theory, it cools your engine more efficiently than an antifreeze/water mix. In practice, however, it is not so simple.

In the old days of cast iron engines, people used to buy corrosion inhibiter rather than antifreeze if they lived in the south. I have not seen that kind of water treatment in a while, I expect because the water pumps and seals and metals are designed with antifreeze in mind.

As someone else pointed out, water without the proper corrosion inhibiters will eat through an aluminum head fast.

Bottom line - don’t take chances with your Audi engine. Use antifreeze at close to the standard 50/50 mix. Use distilled water if your water is ‘hard’. Avoid the so-called “long life” antifreezes. Change your antifreeze every two or three years to get fresh corrosion inhibitors.


Water has a higher specific heat (absorbs more heat per degree temperature rise) than an antifreeze/water mix

Are you sure you got that right? It was my understanding that it was the opposite.


Yup, I’m sure.

The specific heat of a water/ethylene glycol mix is the average of the two liquids, or the weighted average if the mixture is not 1:1.

The freezing and boiling point changes are not simple mathematical ratios because we are dealing with a solution, but the specific heat is a simple ratio calculation.


Theory meets practice: After the water boils (it cools quite well while boiling), it becomes steam, and steam does not cool very well. Many engines have much trouble when there are gas bubbles in the cooling system. It is best to avoid them. Use the correct mixture.


That’s why you need a surfactant added to the water to prevent localized boiling and promote heat transfer. One such product used by racers is ‘Water Wetter’. This stuff also has some other additives for corrosion protection etc.


About three weeks ago my car started rapidly leaking coolant. Since then I have been using mostly water to keep my car cool because I do not have the money to fix it right now. Then a few days ago I started having trouble getting my car started and today it died while it was idling. Could the water have caused all of these problems in such a short amount of time?


[b]Ow! Di! (Audi)[/b]

What are your outside temperatures like? Is it getting below freezing where you operate this car?

Straight water (no antifreeze/antiboil) will boil and create steam at lower temperature than the proper mix. This is exactly what you don’t want if you have a leak. One who cannot afford antifreeze cannot afford to drive. Now you have the problem of not being able to drive and possibly more damage to your car than you had when it just leaked, but ran.

“Could the water have caused all of these problems in such a short amount of time?”