The auto industry is hoping to teach consumers new math: Eight will be six, six will be four, and now four can be three.

Ford Motor Co. this week pulled the wraps off what it says is the smallest engine it has ever built: a three-cylinder, 1-liter engine destined for a Ford Focus next year.

The engine is shorter than a legal size sheet of paper, but Ford promises consumers they won't feel any difference from today's 1.6-liter engines when they step on the accelerator. The engine will produce 118 horsepower, compared to about 70 horsepower per liter on existing Ford four-cylinder engines, the company said.

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Using sophisticated electronics and turbochargers that squeeze more power from a gallon of fuel, Ford, Volkswagen AG and other auto makers are out to challenge one of the key tenets of marketing cars through the years: There's no replacement for engine displacement.

Volkswagen is already marketing its three-cylinder Up compact car using a variation of the slogan from its 1959 U.S. launch of the Beetle. Along the streets around the Frankfurt auto show this week, VW has signs that read, in German, "small is big."

VW Chief Executive Martin Winterkorn said the Up is a key model for the company's plan to grow in the strategically important small-car segment. There will be versions tailored to the individual markets across the globe, such as India.

BMW AG recently showed its i8 concept car with a three-cylinder engine that is used to supplement the battery.

Selling a three-cylinder car in the U.S. could prove challenging. U.S consumers may be migrating away from V8 and V6 engines but the last time a three-cylinder was sold in the U.S. dates back to the 1990s with the Suzuki Swift and General Motors Co.'s Chevrolet Metro. GM dropped the Metro brand in 1997 as gasoline prices dropped and Americans' buying preferences moved to sport-utility vehicles and bigger cars.

"It will be tough," said Chrysler Group LLC Chief Executive Sergio Marchionne. "I know lawn mowers that have more displacement."

But Ford's top marketing chief Jim Farley said the move to small is on and the shift to smaller engines will be dramatic over the next several years. Its engine uses turbocharger and cast-iron block for performance.

"When I look at customer data in the U.S., I have never seen fuel economy more important than it is now," Mr. Farley said. "Fuel prices go up and down but customers now know at any time it could go above $4 a gallon."

Ford has witnessed this cylinder migration first hand. In August alone, 57% of the F-150 pickup trucks sold were equipped with V-6 engines over the V-8 version. Two to three years ago, almost no F-150s were sold without an eight-cylinder engine.

Andrew Fraser, gasoline powertrain director at Ford of Europe, said attracting customers to the three-cylinder will all come down to what he called the "and" factor.

"They don't have to compromise and they will get better fuel economy and they will get more power," Mr. Fraser said. "It is that `and' mentality."

Luxury car makers are also seeing a shift. Adrian Hallmark, global director of Jaguar Land Rover's Jaguar brand, says sales of the big Jaguar XJ sedan in China have increased to a pace of 4,000 a year from just 400 sold in 2010 since the company began offering a six-cylinder engine. Jaguar has also begun offering a 2.2 liter, four-cylinder diesel engine in its European XF models.

"We're not immune to the downsizing trend," Mr. Hallmark says, even though "Jaguar is a V-8 brand."

Jaguar's show car at the Frankfurt show: A low, fast-looking two-seat coupe called the CX-16 equipped with a six-cylinder engine with an electric booster to goose acceleration.