Stick with a genuine GM one - some of the aftermarket ones are not made to the GM temperature specs apparently (GM is expensive so some use some of the GM parts suppliers on the web which are substantially cheaper).

 

What is the most economical way to buy coolant? According to 2011 Chevrolet (USA) HHR Wagon full range specs I will need 7.4 U.S. qt for LT. This is around 2 gallons.

If I get Prestone Dex-Cool Extended Life Antifreeze/Coolant, 1gal - Walmart.com and mix it with 1 gallon of distilled water I should get exactly 2 gallons.

Will this be plenty to do the job or I may need a little extra to top it up? I know for a fact that 5 qt of motor oil is never enough for me when I am doing oil change. Always have to add a little extra to top up the system.

What is the most economical way to do it, so I don't throw 3/4 of a gallon of perfectly good coolant away?

 

Well first... Be careful topping up during oil changes. 5 quarts is PLENTY for our cars. Adding more can actually cause more harm than good. For easy of use just buy the premixed DEXCOOL. When all is said and done be sure to burp the system, as some on here seemed to have skipped that step and end up with overheating issues and such. Some might recommend you change the thermostat but thats up to you. Keep the extra coolant. I might start a feiry debate but coolant DOES NOT HAVE A SHELF LIFE. If you keep it in the bottle, sealed, and away from the elements, then it will not break down or degrade.

 

i replaced my coolant in my 2010 about 6 months ago, (i went a little farther on years, but had less than 150k miles) coolant looked decent, but was over due as far as time wise. no issues at all. i would go ahead and do it, it's alot easier to do some preventative maintenance now, than pay huge repair bills down the road.

 

Yes you will have two gallons of coolant/water which is more than enough to do a full fill. Don't make it more complicated than it is. Just fill with 3.7 quarts of the coolant, and top off with water. That will give you the 50/50 mix required.

The remaining .4 quart of coolant - add .4 quarts of water to it, and use that for top-ups later.

Tip: if you are running the engine during the flush/fill, make sure you do not run it without coolant or water topped up, as running the water pump dry will toast the water pump seals very quickly.

 

If you're gonna mix your own 50/50 mix of Dexcool and water , make sure you use distilled water! Chemicals like chlorine and fluoride don't play well with aluminum engine internals.

 

DexCool does. Somebody a few years ago posted a technical article testing DexCool over time. At 5 years it was not doing the job. Obviously, I can't find it now.

Frequently Asked Questions | Prestone®

The way the answer is written there is a shelf life of "many years" i.e.: 5 years.

If the temp has ever gotten over 240F or or so DexCool tends to crystallize and get clumpy. I assume it is attempting to plug leaks, but it stays that way until flushed and replaced. (personal experience)

Here is an excerpt from WIKI:

 

Found this, from ACDelco. Long shelf life: storage-stable for 8 years... Use this product within 8 years of storing. Use clean drinking water to dilute as impurities in the water can cause a reaction to the coolant and harm the cooling system. Deionized water is recommended.

Dex-Cool Antifreeze | ACDelco

Drinking water, distilled or deionized will work, but deionized is best. Avoid hard water for sure.

 

Thanks for bringing this up. Reminds me that I'm well over due on my '07 even though it's only at 61k.

 

Time is the factor not mileage. I just looked at a low mileage 2007 2LT , sadly the owner had not addressed the cooling system and you could see the chunks in the tee int He upper rad hose, because of this I passed on the HHR