Thanks to American preferences for less-efficient larger trucks and SUVs, the average fuel economy for new passenger vehicles purchased has stayed stuck at 25.1 mpg for the past three model years.

This is based on data from researchers Michael Sivak and Brandon Schoettle of the University of Michigan Transportation Research Institute, which documents window sticker values of new vehicle purchases.

The UMTRI’s monthly monitor, as discovered by Autoblog, shows that fuel economy for light-duty vehicles sold in the U.S. during the 2016 model year was at the same level as the previous two model years.

Hybrid electric vehicle sales haven’t picked up much of the slack. HybridCar’s Dashboard reported that hybrid sales were down from 2015, making for 1.99 percent of total new vehicle sales in the U.S. last year.

Plug-in electrified vehicles had an increase in 2016 to 0.9 percent for calendar year 2016, helped along by a strong few months including an all-time best month of December recording nearly 1.4 percent of new PEV sales.

Still, the sales volume for hybrids and plug-in vehicles hasn’t been high enough to bump up the natural fuel economy average by very much.

Fuel economy - December 2016

CAFE has improved since UMTRI started tracking the new vehicles sales data in October 2007. The university reported that the 2008 model year had 20.8 in average mileage.

Automakers will be watching to see what the Trump administration may do about the “54.5 mpg” by 2025 mandate – which actually amounts to maybe 37-38 mpg on window stickers. The Obama administration and the U.S. Environmental Protection Agency had upset auto executives with its decision to stay with the original timetable and cut off the public comment period much sooner than had been initially stated.

The EPA changed that timetable for the comment period on 2022-25 model year vehicles. What was originally going to be open for comment before review in 2018 was closed on Dec. 30 of last year – a move interpreted as a counter to future plans by Trump’s EPA to potentially weaken standards.

Even so, automakers are hoping the new administration will open up that comment period again, or will consider lightening up the federal mandate through legislative action.

Automakers have been pleased to see the National Highway Traffic Safety Administration ease up the process a bit. Last month, NHTSA postponed a penalty increase that would have been applied to 2015 model-year vehicles. Penalties against automakers not meeting compliance will be held off until 2019.

The federal agency last month also granted automakers’ request for a rule-making process that will help to sort out the differences between the greenhouse-gas standards imposed by the EPA and the fuel-economy standard set out by NHTSA.

Autoblog GreenUMTRI