The Most Rusted List.
I have a 1979 Monte Carlo with the original radiator fluid. The car has 92,000 miles. I check the fluid each year and it registers about minus 15 degrees Fahrenheit. My friend insists I must change the fluid. Is there any need?
RAY: Not anymore, Don. I suspect the American Association for the Advancement of Engine Corrosion has already put you on its Most Rusted List.
TOM: Actually, a lot of people believe that they can just leave antifreeze in their cars forever. The reason, I think, is that for many years, the people who made the stuff labeled it "permanent antifreeze." What THEY meant was that you could use it in both summer and winter. But people thought they meant you could just leave it in there permanently.
RAY: Ah, that's a lot of baloney, Tom. The word "permanent" isn't confusing anyone. Most people are like you--they just forget to change the stuff.
TOM: Yeah, I guess you're probably right. Anyway, the reason you should change your antifreeze every couple of years has nothing to do with keeping your engine from freezing. The real problem is rust.
RAY: Think about it. You've got antifreeze and water running around inside a metal engine. And what do you get when you mix water and metal? Rust!
TOM: So all antifreeze contains chemicals that prevents that rust from forming (they're called rust inhibitors). But the rust inhibitors are only good for a couple of years.
RAY: So when you change the antifreeze, you not only renew the rust inhibitors, but you also drain out all the particles of rust that have started to form so they can't plug up the small passages in the cooling system.
TOM: At this point, Don, you've probably got a nice little rust farm developing inside that Monte Carlo's engine. If I were you, I'd not only change the antifreeze, I'd also get a power flush, which cleans out the cooling passages under high pressure.
RAY: Then cross your fingers, and hope that the rust doesn't clog up your cooling passages. Because if it does, you may have to give the entire Monte Carlo the power flush.