Many years ago, when I was fresh out of school working in Denver, I was driving to my parents’ home in Missouri for Christmas. I stopped at a gas station about 50 miles from Oklahoma City, where I was planning to stop and visit a friend. I pumped the tank full, stood in line at the cash register, and said hello to an older couple who were also paying for gas.
I took off, but had gone only a few miles when black smoke poured from my exhaust pipe. I pulled over and wondered what I should do.