The Environmental Protection Agency is more ambitious for the next phase of its heavy-duty truck fuel economy standards than it was for the first.

Christopher Grundler, director of the EPA Office of Transportation and Air Quality, said that while it’s too early to spell out details, the agency will look at trailers as well as new engine and transmission technologies.

In remarks Wednesday morning to fuel and transportation experts gathered in Washington, D.C., for the Alternative Clean Transportation Expo, Grundler said the agency also will look at aerodynamics, alternative fuels and the legacy fleet.

Grundler was discussing the issue in the wake of President Obama’s announcement yesterday that EPA will develop new fuel economy and greenhouse gas standards for post-2018 model year trucks, following on the standards that were put in place in 2011.

“We are talking to manufacturers and we’re very excited about the technologies they are working on for the future,” Grundler said.

“The technologies span the gamut from better engines to better transmissions, to better aerodynamic designs to mass production to fuel-based strategies. All of that will be on the table for consideration as we begin this collaborative process.”

He said the agency intends to build on the “substantial amount of good will” generated by the effort that led to the 2011 standards.

“Everyone embraced these standards because we worked collaboratively,” he said. “It was remarkable what we achieved.”

Still, he said, the agency is setting higher goals for the next round. “It will be more challenging and more difficult to achieve, but worth while. There are still cost savings that are available to customers that we would like to see.”

He said the agency will follow the same process this time around: engage the stakeholders early on, keep them involved and listen to the opportunities they see as well as their concerns.

Meanwhile, the agency is focusing on implementing the 2011 standards, he said.

Those standards will lead to significant fuel savings. Grundler said that by 2025, the U.S. will be using 2.1 million barrels less oil per day than it does now – more than was imported from the Persian Gulf last year.