Facing stricter fuel economy standards, BMW and Mercedes-Benz are considering bringing four-cylinder engines back to the United States.

BMW stopped offering four-cylinders in 1999 when its 318ti hatchback flopped. Mercedes-Benz had four-cylinder engines on the 2005 C230 and SLK230 but dropped them in favor of six-cylinder models.

BMW of North America is considering a twin-turbocharged, direct-injection four-cylinder gasoline engine for U.S. vehicles, said CEO Jim O'Donnell.

"The plans will be firmed up when we have definite news from Washington on what the fuel standards are going to be," he said.

O'Donnell said the engine could be used in 1- and 3-series cars and the X1 and X3 crossovers. BMW is designing the four-cylinder to have as much power as its current inline six-cylinder family, but with better fuel economy and lower emissions, he said.

One potential snag: The four-cylinder costs more to build than the six-cylinder family, and BMW would pass along that cost to consumers. O'Donnell said buyers may not be willing to pay more for advanced technology.

Mercedes-Benz is deciding whether to offer the four-cylinder diesel from the E250 Bluetec concept at the New York auto show this month.

The show car, based on the new E-class sedan, has a 2.2-liter four-cylinder diesel with 204 hp and a fuel economy rating of nearly 40 mpg on the highway.

Ernst Lieb, CEO of Mercedes-Benz USA, said the E class may not be the right car for the engine in the United States. But, he said, it is well-suited for the C-class sedan and GLK compact SUV and could be used in the current generation of both vehicles.