Coolant dilution

I was recently told that I’m probably damaging my engine (or radiator?) by adding coolant undiluted, that I should get a little gizmo to check the dilution & add water. (I recently was adding some when it got low. This is about all I normally do.) I looked at the container it came in, & to my surprise does say to use 50%-70% coolant, with distilled (or “purified”) water. That would mean I’d have to know how much I was going to add & measure it. Is this really necessary? (I add when it gets low, taking the overflow tank up to the appropriate level.) Thanks.

Yes, it really is necessary to get the maximum protection from the antifreeze.
The easy way out is to buy it premixed.

Yes, it’s necessary. Pure coolant freezes at a higher temperature than a mix, which surprises many people.

However, you should investigate why you keep needing to add coolant. A properly running car doesn’t use coolant. The worst case is if it’s getting into your oil, which will eventually kill your engine. Does your oil look normal and not milky?

If the concentration of antifreeze gets too high in the cooling system it can result in gelling of the antifreeze which will cause overheating of the engine. This is probably one of the easiest coolant testers to use With this you’ll be able to determine if the concentration of antifreeze is getting too high. If it does, just start adding straight water to the cooling system until the tester reflects optimum protection.


Thank you all!

I think I gave the wrong impression. I recently found it quite low. (The “check coolant” light came on. In this car, seeing how much is in the overflow tank isn’t all that easy, & I don’t habitually pay that much attention.) Before that, it had been a good number of years since I’d added any. I do need to keep an eye on it, but it’s not like it has any history of needing filling. If it’s going into the oil or out a radiator leak, it’s probably very recent. (I was very glad, though, that I’d followed someone’s recommendation years ago, to keep some in the trunk.)

Sorry for the confusion. And thanks.

Yep, just add water next time and test the strength.
In general a 50/50 mix is normal.
Nothing to measure with ?
A glug glug of antifreeze…
a glug glug of water…
= 50/50

As your jug of anifreeze gets down half way,
Fill it with water and
– presto –
50/50 :slight_smile:

Then mark that jug as being 50/50 on some masking tape when you set in with your supplies so it is ready to go next time.

Hold on there folks. Dave is loosing coolant. Dave asked a question and it was properly answered but maybe more important was the question Dave did not ask. Why is Dave adding coolant? Dave has another problem since a properly functioning car does not need coolant added.

    [b] Dave, If you get this message, YOU HAVE A LEAK.  That could cause some expensive damage if you don't address it.[/b]

Dave, I work for prestone coolants. you are going to damage your cooling system and possibly cost yourself an engine in the process. When coolant gets too concentrated, it “gells up” and turns to a jello like substance. this plugs cooling passages and can cause engine overheating and blown headgaskets/other issues. You should thoroughly drian and flush your cooling system right now and add the appropriate 50/50 mixture of coolant and water. Buy dionized or distilled water that grocery stores sell for ironing, it works fine.