How often should I change the coolant in my Buick?

Dear Car Talk

Dear Car Talk | Dec 01, 1995

Dear Tom and Ray:

A milk man I had a talk with claims that with these late model cars, the anti freeze has to be changed every two years. I have a '94 Buick Century. A mechanic at the GM plant I retired from says the only thing that goes in these anti-freezes is the rust inhibitor. Who's right, and how often should I change my coolant?

TOM: They're both right, Joe. The "anti-freezing" and "anti-boiling" properties of the coolant should last forever. But there are two reasons to change the stuff more often than that.

RAY: One is that the rust inhibitors do break down. Some people just add some inhibitor to the radiator every couple of years and consider the matter forgotten, but they're missing the second reason why it's important to change the coolant.

TOM: There's junk that collects in the cooling system. There are pieces of crud and little flakes of rust that float around and can eventually clog up the tiny passages in the radiator, heater core, and cylinder head. And fixing those things is very expensive compared to changing the coolant.

RAY: So if you really wanted to be economical, you could drain out the coolant, filter it (we found that running it through a loaf of Wonder Bread works best), and add some new rust inhibitor. Then, theoretically, you could then put it back in the engine.

TOM: And if you own an eighteen wheeler that uses a hundred gallons of coolant, or you're doing this on a large scale and selling the stuff (as some companies do) that might make economic sense. But for an individual car that uses only a couple of gallons of coolant, it's hardly worth the trouble.

RAY: So our advice is to drain the coolant every two years or so. And if you happen to have a can of rust inhibitor and an extra loaf of Wonder Bread laying around, you can go ahead and reconstitute the stuff yourself. But most people find it easier to just add new coolant.

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