NEVER listen to your husband when it comes to cars.

Dear Car Talk

Dear Car Talk | Dec 01, 1991

Dear Tom and Ray:

My husband insists it is OK to use antifreeze only--no water--in our car's cooling system. He says a number of mechanics have told him it's perfectly alright. But the owners manual of our '88 Chevy Nova says to use a 50/50 mixture of antifreeze and water. I'd really appreciate your opinion on this.

TOM: Sandy, our opinion is you should NEVER listen to your husband when it comes to cars. Husbands are always wrong about car stuff. Especially when they "insist" they're right. Trust me. I'm absolutely sure of this.

RAY: Unless you live where they play ice hockey outdoors in the summer, (in which case you can use a 70-30 mixture of antifreeze to water), you should always use a 50/50 mixture.

TOM: Here's why. There are three things you want your coolant to do. You want it to protect against freezing in the winter. You want it to absorb heat to keep the engine from overheating. And you want it to keep the cooling passages inside the engine from rusting.

RAY: Straight antifreeze freezes at about zero degrees fahrenheit. But when you mix it half and half with water, the freezing point DROPS to about 40 below zero! So, believe it or not, you have better protection against freezing with a 50/50 mixture.

TOM: It turns out you also get better heat absorption in hot weather with a 50/50 mixture. Although that's harder to explain in numbers that make any sense to you or me, our Chief Bottle Washer and Staff Thermochemist, Doug Berman has assured us that a 50/50 mixture will absorb more of the engine's heat than straight antifreeze. And although straight water is a pretty good heat absorber, its boiling point isn't as high as the 50/50 mixture.

RAY: The final frontier is rust. Antifreezes contain rust inhibitors, which keep rust from forming in?side the little cooling passages in the engine. If rust forms there, it can block the passages and lead to the automotive equivalent of a hardening of the arteries.

TOM: Here, straight antifreeze would probably give you the best rust protection. But research shows that as long as you have 50% antifreeze in the mixture, the rust inhibitors will do their job just fine.

RAY: So the 50/50 mix really is the optimal mixture to balance freezing point, heat absorption, boiling point, and rust protection. Not only that, but it also saves you 50% on your annual antifreeze bill. So tell your husband that if he uses a 50/50 mix, he'll not only be treating his car better, but he'll also save enough money to take his wife out to dinner more often.

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