What's That Smell?

Oct 19, 2021

It's time for the new puzzler. And as I promised this wasn't going to be as lousy as the last one.

Here it is. There is a smell that comes from modern cars that people associate with the catalytic converter. And I'm going to ask about another smell that comes from modern cars, cars with catalytic converters. So you often get this smell from cars that are equipped with catalytic converters.

But this smell is not coming from inside the converter. It has nothing to do with what's going on inside the converter.

I will give a hint. If cars of fifty years ago had catalytic converters, they would not have made the smell. The smell would not come from these cars. And it has nothing to do with the gasoline. What is the smell and what causes it?


I'm constantly amazed at the ability of our listeners to come up with answers to puzzles that no normal people should know the answer is a testimony to the intelligence of the NPR listening audience.

So now, without further ado, here it is.

Occasionally a customer will come into the garage and complain about a smell.

There is an odor that comes from vehicles that have catalytic converters. And the origin of this is indeed from the converter, but it's not from inside the converter, nor does that have anything to do with the kind of gasoline that the converter that cars that have converters, i.e. unleaded gasoline.

It took us a long time to figure this out the first time we saw it. And I'm sure there are people out there that have had this odor coming from their cars and couldn't figure it out.

What it is, is that a plastic trash bag (and they're everywhere) has your right has stuck to the catalytic converter. And the reason this wouldn't have happened years ago is that there weren't any catalytic converters and there weren't any plastic plastic trash bags.

So the converter is so hot that all a plastic bag would have to do is just come close to it.


Get the Car Talk Newsletter