Will Cataclean help to pass failing emissions smog test?
Maybe, but only if the catalytic convertor is the problem. In other words, if the check engine light is on and the error code set is P0420, it wouldn’t hurt to try some and see if the check engine light goes out. But don’t bet on it.
The 2 times I have failed the emissions test I’ve had other problems (a disconnected choke the first time, a leaky acceleration pump the second), and been better off because I fixed the problem. Using an additive to cheat the test would have cost more than not-fixing the problems. Figure out why and fix the problem: you’ll save money in the long run.
Cat converters lose their efficiency because the catalyst in the device’s innards becomes coated with combustion byproducts that continue to build up even in the constant stream of exhaust gasses and the high temperatures of the converter. The catalyst, platinum-palladium sputter-plated onto a ceramic core, is very porous, and the contaminants become embedded in the surface. You cannot burn these out with an additive.
But I don’t know that any of these magic elixirs cause any harm, so if you’re willing, go ahead and try it. let us know how it worked.