Advanced high-strength steel, the newest, lightest steel invented, is aiming to hold off aluminum’s rise as the metal of choice for an auto industry in the midst of major changes.

Lightweight aluminum has chipped away at steel’s use in vehicles as fuel efficiency standards have risen. Now steelmakers are fighting back. Their newest alloy could make its way to carmakers by 2021, with some available as early as next year, said Eric Petersen, vice president for research and innovation at AK Steel Holding Corp.

The new steel will be marketed as stronger, less costly and almost as lightweight as aluminum at a time of upheaval for carmakers. The fuel standards are under attack, a trade war threatens to hike costs, and the auto industry is racing toward a future with electric cars that consumers insist go further and further on a single charge.

For automakers, “the biggest bang for their buck is going to be in the powertrain and battery supply,” Petersen said. "Once you put your dollars there, you’re better off to go with a lower-cost solution in steel."

Steel has long been the main choice for car parts and remains so today, making up about 55 percent of vehicles on average, compared with about 10 percent for aluminum. But the amount of aluminum in use has been rising over the last three to five years, said Abhay Vadhavkar, head of manufacturing, engineering and technology at the Center for Automotive Research.

In 2014, for instance, Ford Motor Co. introduced a redesigned version of its F-150 pickup truck -- the top-selling vehicle in America -- with an aluminum body, part of a shift Vadhavkar sees as "pretty significant," given it was achieved among larger companies.

Now, change is in the air once again.