CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Wiper & Coolant Fluids

My husband says it is ok to use a windex mixture in the wiper fluid reservoir instead of storebought. True? What’s the ratio? Also, if the coolant is low, using plain tap water is sufficient (we live in Phoenix). True? Thanks!

Since Windex is considerably more costly, ounce for ounce, as compared to jugs of pre-mixed washer fluid, I fail to see the economic sense of using Windex in the washer reservoir. I will leave it up to someone else to comment on whether Windex is safe for automotive paint.

As to substituting straight tap water for the correct 50-50 mix of coolant and water, that is a really good way to wind up with an overheated engine and also to wind up with rust and corrosion in the cooling system. The few bucks that you would save by not buying a jug of antifreeze/coolant with be far outweighed by damage to your engine and cooling system.

I suggest that you find other ways to economize.

If you live in Phoenix, where you almost never see freezing temperatures you can use just about anything for wiper fluid - including just tap water. You may want to check anything you add just to find out what it has to say about its effects on paint.

If the coolant is low you need to take the vehicle to a good mechanic and find out where it is leaking from. This is the only reason that you would ever need to add. If needing to add is a chronic problem then, no - you shouldn’t just add water. You should add a 50/50 mix of the correct kind of coolant and water. It isn’t just “antifreeze” but is also “coolant.” Just adding water over time will dilute your mixture and the cooling system won’t cool properly. This will lead from a small, cheap problem to a large, expensive one (need for a new engine).

You can use diluted Windex. But it’s still far cheaper to use regular washer fluid. It’s only around $1 a gallon. As for the coolant, stick with the 50/50 antifreeze/water mix. You may even want to use distilled water with the antifreeze. Alternatively, if the mixing is too much of a hassle for you, you can buy pre-mixed anti-freeze, but it’s usually a tremendous rip off, size it costs quite a bit more for what you get (50% less actual antifreeze).

Ask your husband if he believes corrosion inhibitors have been added to your tap water. Also ask if he knows how much it costs to replace a corroded radiator.

Since there are several versions of Windex, I would strongly advise against it. It may contain some materials that could damage the washer parts. I don’t think so, but why buy a more expensive fluid when the right one is cheaper and easy to find.

A little water to top the coolant off will not hurt. Doing that more than once or twice could cause problems however.

BTW coolant does more than keeping the fluid from freezing, it also helps the water carry more heat away from the engine and protects the metal parts.

I Phoenix, I would not even use tap water for the 50% of the coolant that is water. Last I knew, the CAP water was in use and that stuff has got a lot of dissolved minerals in it. When I was in Arizona. An R was added to the acronym in common usage.

I would avoid Windex, both from the standpoint of its effect on paint finish (it contains ammonia which removes wax and leaves the finish unprotected from the sun) and its potential adverse effect on rubber bits (seals, grommets and lines).

As for engine coolant, you may not need the added protection from freezing, but coolants also raise the boiling point of water, and you certainly need to protect against overheating where you live. Beyond that, commercial coolants contain corrosion inhibitors which are beneficial to keeping the radiator core clean, free of mineral buildup, and functioning effectively to transfer heat out of the engine. Tap water can’t do that.

Do NOT use Windex. Windex contains ammonia. The washer fluid will spray on the window and will run down the window into the air vents…thus you’ll bring the ammonia gas into the cabin (i.e. the air you breath). I guess it would be OK if you drove around with the windows open.