A Puzzler of Yore

May 31, 2022

So, something happened the other day and I was reminded of a puzzler from a while ago. A puzzler of yore, as they say.  It was many, many years ago that we use a puzzle that was similar to this and I was reminded of it just the other day when a customer came into the shop. He had gasoline leaking under the hood of his car. Yeah. It was an older car, some old jalopy ready for the boneyard. Like a 1963 Dart! Ha! 

Kidding. I don't remember what kind of a car it was, but it was a Toyota, I believe. And the fuel line that ran from the pump to the carburetor was leaking and gasoline was in fact leaking onto the hot exhaust manifold. He was extremely agitated. And he said, "You've got to fix this immediately because my car is going to catch fire because it's leaking gas onto this hot manifold!"

So I opened the hood. And of course, the smell of gas was everywhere. When I opened the hood, I found the leak and I fixed it.

He said, "Thanks very much. How many hundreds do I owe you? And also, by the way, why didn't it catch fire? I was worried about it was going to catch fire. But it didn't. Why?"
And I said, "Well if it caught fire, we wouldn't have made any money because we don't do fireworks!"

So this is the puzzler. 
Now, I will give you some little hints here. The ignition point of gasoline, the point at which gasoline catches fire is about 700 degrees Fahrenheit. The temperature of the hot manifold onto which the gasoline was dripping? It's probably also 700 degrees. Maybe even a little bit more.

So, why didn't the gasoline catch fire?



Okay, an answer to the Puzzler of Yore! 

Everyone knows that gasoline and heat make fire. It happens inside the cylinders all the time. So, I opened the hood, and there was this little hose that was leaking gasoline on the manifold. So, I changed it out, and charged him way too much... Ha! Anyway, he asked me why it didn't catch fire. So, fun fact. This same customer had spilled motor oil on the manifold in the past. Thick motor oil. And it did catch fire. But the gasoline didn't. And he wanted to know why, because they even have the same ignition point. 

So the reason the gasoline doesn't burn, is that it doesn't stay around long enough! 

The gasoline vaporizes so readily that as soon as it gets even close to the manifold, it starts turning into a gas and it disappears. So, it never gets hot enough to ignite, because it is already gone. And the vapor doesn't ignite because it's too far away from the source of the heat. The motor oil, which is thick, and doesn't turn into a gas, will ignite. 

So, there you have it. 


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