Why isn't silicone braking fluid more widely recommended?

Dear Car Talk

Dear Car Talk | Oct 01, 1992

Dear Tom and Ray:

You recently recommended to a reader that she change the brake fluid in her car every 30,000 miles or about every two years for most drivers. I have three older cars in which I have put silicone brake fluid. Silicone brake fluid has a higher boiling point, and doesn't absorb moisture like ordinary brake fluid, so it never needs to be replaced. It's more expensive--about $14 a quart vs. $3 a quart--but it is a far superior product. Why isn't it more widely used?

RAY: Like you said, Wes, it costs more than four times as much as regular brake fluid. And while it does have some superior characteristics, most drivers would never notice enough difference to justify the price.

TOM: While the higher boiling point of silicone brake fluid may be advantageous--or even necessary--for people who tow trailers or drive Porsches, it's overkill for the average driver.

RAY: Right. You could install an exhaust system that was made of 14 carat gold, and that would be great, because it would never rust. But you could install a regular exhaust system many times over, and buy exhaust systems for all your neighbors, before you equaled the cost of one golden tail pipe.

TOM: And if you do the math, you'd have to keep the silicone brake fluid in your car for over 140,000 miles in order to come out ahead in terms of dollars. And that's assuming that you don't spring a leak because a flex hose brakes, and spill $20 worth of break fluid in the K-Mart parking lot. And that's as likely to happen with silcone brake fluid as it is with the cheap stuff.

RAY: So the advantages of silicone brake fluid aren't really as obvious as you suggest, Wesley. I DO like the golden tail pipe idea. Don't you?

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