Zach Rodriguez tries to practice what he preaches, which is why he reprogrammed his mother's oven to display 180 degrees Celsius, rather than 356 degrees Fahrenheit.

The 19-year-old college student from San Antonio wanted to make a poundcake. But he is a firm believer in the metric system, so baking in Fahrenheit wouldn't do. He "metricated" the oven using "a complicated, nonintuitive sequence of button pressing," he says.

Mr....