REARDAN, Wash. (AP) — 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 only count up to $99.99 for the total sale, preventing owners of some SUVs, vans, trucks and tractor-trailers to fill their tanks all the way.

As many as 8,500 of the nation’s 170,000 service stations have old-style meters that need to be fixed - about 17,000 individual pumps, said Bob Renkes, executive vice president of the Petroleum Equipment Institute of Tulsa, Okla.