Can I add rust inhibitor to my antifreeze?

Dear Car Talk

Dear Car Talk | Sep 01, 1989

Dear Tom and Ray:

I've heard you guys talk about antifreeze and the need to replace it every year or two because of radiator rusting. Antifreeze is getting so expensive that I was wondering if you could just add a small can of rust inhibitor to prevent rusting?

TOM: Antifreeze certainly is getting expensive. If you were a subscriber to the CAR TALK Investment Newsletter, you'd have noted that last month we recommended selling your Pork Bellies and buying Antifreeze Futures.

RAY: But Henry, it's not the radiator rusting that's our concern. Most radiator rusting is the result of external factors such as road salt. Our concern is engine rusting. The antifreeze and water travel through small passages in the engine block, which is made of iron. Little flakes of rust can eventually clog up these passageways, so the reason for draining the antifreeze is to drain the rust particles. The antifreeze itself will last forever, and you can re-use it if you pour it through a strainer first, and then add a can of rust inhibitor before putting it back.

TOM: Our cousin Vinnie says that the best way to strain the rust is to pour the antifreeze through a loaf of stale Italian bread. That may be true, but I'll never eat another sandwich at his house!

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