I love the internal combustion engine. One of my first cars was a gas-guzzling V-8 Mustang. Today's itsy-bitsy four-cylinder gas misers are certainly more practical. But if you want to hear me giggle like a little girl, put me in the seat of a 650-horsepower Shelby GT500. Watch as I shtail the car, sprint to 100 mph, stomp the brakes, then do it again.

But here's the sad reality. The day will likely come when the earth runs out of affordable crude oil. It could be 50 years from now, or it could be 300 years. On that day, a Jaguar convertible, a Hummer, even a Lamborghini will be of little practical value. What good is a powerful gasoline vehicle, if the world has no fuel?

The fossil fuel crisis may be centuries away. But the evangelical fuel crisis—the crisis of donations—is already upon us. And it will only grow more severe in the future. Senior citizens comprise 19 percent of church attenders, but they account for 46 percent of all donations. As members of this generation die, ...