As automakers unveil smaller electric cars and hybrids at the New York International Auto Show this week, Volkswagen’s President and chief executive insists the industry not only should develop those vehicles, but also improve fuel-efficient gas and diesel models.

Stefan Jacoby, head at Volkswagen America said he is confident that as Americans become more educated on the benefits of clean diesel vehicles, these cars will gain popularity. Jacoby said drivers can get from 20 to 40 percent better mileage with diesel fuel, together with 50 percent more power but it is still more expensive than gas in the U.S.

We have to be realistic and honest about the future of alternative fuels, Jacoby said according to the Associated Press. We still have challenges in making these vehicles affordable and reliable, citing that traditional gas and diesel vehicles are reliable in extreme weathers but it is not proven the same for battery-powered ones.

Meanwhile, Honda and Ford unveiled new cars at the Auto show, known as the Insight and Fusion Hybrid respectively, while Chevrolet introduced its Volt.

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