German automakers stressed their low-emission credentials at the Frankfurt auto show this week, displaying a range of battery-powered cars.

That is no surprise given the cloud over diesel technology that has grown since Volkswagen admitted to rigging diesel cars to evade U.S. emission testing. That was worsened by the discovery that other carmakers in Europe had exploited legal loopholes to turn off emissions controls much of the time — so that real-world driving emissions were much higher than test results.

Yet carmakers insist that diesel will continue to play a role. Experts say they may be right.