DETROIT – German auto makers will collaborate on a “buy diesel” campaign in the U.S. as they look to spur interest in the engines as fuel-efficient, cost-effective alternatives to hybrid-electric vehicle technology.

And they are eager for other auto makers to join the marketing drive.

Speaking here at the North American International Auto Show, Matthias Wissmann, president of the German auto makers’ manufacturing association, the VDA, says his members increased sales of clean-diesel vehicles in the U.S. 40% last year to about 110,000 units.

Diesel-car sales grew 34% to more than 75,000 units last year, while diesel-truck sales jumped 50%, he says.

“For years now, the German manufacturers have taken 100% of the market for diesel passenger-cars – so the growth was all to the benefit of the German makes.”

The diesel marketing push will get under way “this spring or summer at the latest,” Wissmann tells WardsAuto.

Each auto maker will craft its own advertising, but as a group they’ve agreed to include consistent messaging that will “hammer it into the consumer how efficient and economical the diesel is,” he says.

The VDA is actively encouraging other auto makers join the campaign.

“We don’t want this to be a pure German thing, because we know some of our Asian competitors are considering the same thing,” Wissmann says.

Diesels have not been granted the same extra credits in upcoming U.S. corporate average fuel economy rules that hybrids and electric vehicles enjoy, but the VDA won’t be campaigning for a change in the rules, preferring to leave that up to U.S. manufacturers groups.

Overall, German car makers sold more than 1 million vehicles for the first time in the U.S. in 2011, an 18% increase from 2010 levels that far outpaced the 10% growth for the industry, Wissmann notes.

This year, the VDA is projecting total U.S. sales to rise 5% to 13.4 million vehicles, and Wissmann says the Germans are likely to increase their share “for the eighth year in a row.”

“The 2-pillar strategy that our manufacturers are pursuing on the U.S. market of increasing both exports from Germany and local assembly here in the U.S. is paying off,” he says, noting the Germans built close to 1 million light vehicles in the North American Free Trade Agreement region last year, up 40% from 2010.

Some 540,000 vehicles were exported to the U.S. from Germany last year, Wissmann says. Another 100,000 units were shipped here from automotive plants outside Germany and NAFTA.

“Receiving 12% of all German car exports, the U.S. is one of the three most important export partners for the German automotive manufacturers.”

Wissmann says he is uncertain what will happen in Europe as governments wrestle with debt issues and try to keep the euro region united. But he says the weakening currency could help the Germans sell cars in the U.S.

“With all our capacity in NAFTA now, the currency swings don’t have as big an effect as they used to,” he says. “And certainly, (the weakening of the euro) isn’t something we would want.

“But it could have a positive effect.”