Like a lot of small-scale entrepreneurs, Cathy Osborne worries that she’ll go out of business if fuel prices rise above $4 a gallon. Not because she won’t be able to buy gas at that price, but because she won’t be able to sell it.

The old mechanical gas pumps with scrolling dials at her country store in Fauquier County, Va., lack the gears to go beyond $3.99 a gallon. State inspectors shut down her diesel pump several months ago when the fuel topped the $4 mark, so now all that’s left are two pumps dispensing 87-octane gasoline, set at $3.75 - and climbing.

“I don’t know what I’m going to do. I don’t have $30,000 to invest in new pumps, and I’m barely skipping by,” said Osborne, who owns the Orlean Market and Restaurant, a store dating from 1892 with horse-country views of the Blue Ridge Mountains and miles of rolling Virginia Piedmont.

Osborne said she doesn’t make money on fuel sales, but the pumps are a big draw for the hay farmers and cattlemen who gas up their tractors and take their morning coffee in her store. The next-closest service station is a 40-minute round-trip drive to Warrenton, and in Orlean, Osborne’s barbecue sandwiches and Amish-baked cherry pie face no competition.

“If people have to go into town to get gas, they’ll say, ‘Oh, I’ll just go to Burger King,’ “ Osborne said.

At gas stations in metropolitan areas, digital screens and electronic credit-card readers are standard, but in tiny communities such as Orlean, about 60 miles west of Washington, many mom-and-pop markets are pumping in analog. The dispensers are reliable and retro-cool to some, although their designers apparently never contemplated a future with $127-a-barrel oil.

“We’re one of the few that are left,” said Sharon Hammett, owner of Piney Point Market in St. Mary’s County in Maryland, who said her customers are mostly local watermen. “If it gets too bad, maybe we’ll just pull” the pumps out, said Hammett, unnerved by a recent TV program with apocalyptic predictions of $8-a-gallon gas.

About 8,500 of the 170,000 service stations in the United States are using mechanical pumps, according to the Petroleum Equipment Institute, a trade group based in Oklahoma. Most are in out-of-the way rural areas or at marinas, and not, said executive vice president Robert Renkes, “in the middle of downtown Washington.”

Regulators take a dim view of the obsolete machines, no matter how quaint their surroundings, if the spinning numbers don’t accurately reflect what’s going into gas tanks.