Full-size pickup trucks, some of the biggest sellers for the Detroit Three automakers, will be able to meet less stringent fuel economy standards than cars from 2017 to 2021 under the proposed Corporate Average Fuel Economy standards announced by the government Friday.

The standards would raise the average fuel economy ratings of cars to 54.5 miles per gallon by 2025 beginning in model year 2017 by increasing annual mpg targets by about 5% annually. The standards for pick-ups and other light-duty trucks would rise 3.5% annually through the first five model years and then 5% annually after that, according to the initial proposal.

Thirteen automakers, with Chrysler LLC, Ford Motor Co. and General Motors among them, agreed to the proposal, which effectively doubles fuel economy standards from the current 27 mpg.

Daimler AG and Volkswagen AG did not sign the agreement. Volkswagen said the “positive impact” of so-called clean diesel, used by the company’s mid-size Passat TDI, which can get 43 mpg on the highway, doesn’t receive consideration in the proposal, Volkswagen said, according to Bloomberg News.