Consumer options for light duty diesel vehicles are expected to be slimmer next year. The U.S. Department of Energy and EPA released its preliminary 2018 Fuel Economy Guide, which lists just 11 light duty diesel vehicles, with 21 models from five manufacturers represented. In contrast, the 2017 guide listed 28 models from eight manufacturers. This is a sharp drop from 2015, when 32 models from eight manufacturers were listed in the guide.

With a rising number of offerings, Jaguar Land Rover has four models listed, and expects to add another model to the list for 2018. However, Jaguar Land Rover is one of only a handful of manufacturers on the list. Mercedes paused its US diesel plans this year, making BMW the sole German manufacturer currently listed for 2018. Chevrolet and GMC round out the list of current manufacturers in the guide. The rumored Mazda CX-5 is not yet listed, and the Jeep and RAM 1500 diesel vehicles are also not yet included.

Heading into 2018, automakers across the board have reported more challenges in obtaining vehicle certifications. According to Bloomberg, Daimler AG “cited the ‘increased effort’ needed to obtain approvals from U.S. environmental regulators as a key reason in halting efforts to obtain the necessary certifications” for Mercedes vehicles. Earlier this month, Porsche announced delays in delivery of 2018 model year vehicles which were ”still in the final regulatory approval process.”

The approval process could become even more complicated if the EPA and California Air Resources Board diverge over future fuel economy and emissions standards, as threatened in recent months. For now, it will be interesting to see which, if any, additional manufacturers and models clear the certification process for 2018.