BMW to offer four-cylinder diesels in North America to improve fuel efficiency

BMW will offer four-cylinder diesel engines in North America as it seeks to improve fuel efficiency and match the performance of its current six-cylinder gasoline engines.

BMW is considering diesels in a range of models, including its 1 series, 3 series and 5 series sedans and possibly the X3 crossover and Z4 roadster, said Tom Baloga, vice president of engineering for BMW of North America.

"You're going to see it in the 3 series, and the 5 series is a good possibility," Baloga said. "If the performance is sufficient in the X3, U.S. customers would likely accept it in the X5 as well."

Baloga did not disclose timing but said BMW will be ready to comply with emissions rules. Federal rules will regulate the amount of carbon dioxide per mile, based on an automaker's fleet average. The rules call for an average of 250 grams of C02 per mile by 2016, which equates to 35.5 mpg.

Baloga said BMW will seek diesel performance comparable to that of its current six-cylinder engines by using a turbocharged 2.0-liter model tuned for performance. In Europe BMW sells a 320d with a 2.0-liter turbocharged diesel.

"Our four-cylinder diesel will be so good that people will readily accept it as a replacement for six cylinders," Baloga said. "With the weight reduction, performance could be similar to the turbocharged six-cylinder [gasoline engine] if we pushed very hard."

Baloga said BMW will aim for a substantial increase in its diesel sales mix in North America.

"If we hit 10 to 20 percent, we would be happy," he said.

In Europe, 70 percent of BMW's sales are diesels.

With exhaust treatment, BMW's diesels will meet California emission standards as well as federal tailpipe emission rules. Baloga didn't disclose what technology would be used -- a diesel particulate filter or a selective catalytic reduction treatment with a refillable on-board urea tank as in the BMW 335d.

"The strategy for aftertreatment is to make it less expensive and less trouble," he said.

Unlike archrival Mercedes-Benz, which began selling diesels here in 1960, BMW waited until this year to introduce an ultraclean 50-state diesel engine. BMW's only prior U.S. diesel was the 524td, sold as a 1985 model.

BMW discontinued the model after selling 3,644 units in the United States. Demand fell off, and the reputation of diesels became tainted in the United States because of problems associated with diesels offered by General Motors in the 1980s.

Sales of the X5 xDrive35d and 335d, which are powered by a 3.0-liter, twin-turbo, six-cylinder in-line diesel, got off to a slow start. Diesels now represent 13 percent of total X5 sales but only 1.3 percent of 3-series sedan sales.

BMW launched a marketing campaign and offered a $4,500 rebate on both diesels during last summer's cash-for-clunkers program. The incentive continues through December. Through October, BMW sold 1,002 335d sedans and 2,706 X5 xDrive35d crossovers.

The 335d has an EPA rating of 23 mpg city/36 mpg highway -- 35 percent higher than the gasoline-engine model. The X5 xDrive35d is rated at 19 mpg city/26 mpg highway. BMW says the vehicle's performance is comparable to that of a gasoline V-8 engine but fuel economy is 37.5 percent better.

By Jason Stein and Diana T. Kurylko- Automotive News