A quote from the link helpfully provided by the prior poster.

"His gas mileage was about 19 mpg when he purchased his five-cylinder 2005 Chevrolet Colorado. Now, with the engine broken in and new tires filled with nitrogen, he gets 20.5 to 22 mpg depending on whether he runs the air conditioner, he said."

So, did the increase in mileage result from the engine break-in or the nitrogen? (You can give only one answer and it better not be nitrogen!)

And the guy being quoted is an engineer? Sheesh!

The nitrogen might reduce the rot (a bit).

The only clear, measurable benefit of using nitrogen is to the person selling it!