The $3.99 problem:

Mom-and-pop service stations are running into a problem as gasoline marches toward $4 a gallon: Thousands of old-fashioned pumps can't register more than $3.99 on their spinning mechanical dials.

The pumps, throwbacks to a bygone era on the American road, are difficult and expensive to upgrade, and replacing them is often out of the question for station owners who are still just scraping by.

Many of the same pumps can count only up to $99.99 for the total sale, preventing owners of some SUVs, vans, trucks and tractor-trailers from filling their tanks all the way.

(Via Marginal Revolution.)