Ford demonstrated its obsession with shedding weight Tuesday in San Francisco with a concept car that looks like a Ford Fusion but uses parts made of aluminum and other lightweight materials.

It applies lessons learned from the 2015 F-150 aluminum body and represents the third phase in a larger plan to improve fuel efficiency with advances that can be applied in nearly every vehicle in its lineup.

Reducing weight has never been more important as consumers demand performance and the latest technology, while the government requires much better fuel economy.

Phase One of Ford’s Blueprint for Sustainability, launched in 2007, focused on its EcoBoost family of turbocharged engines. Phase Two centers on lightweighting. Phase Three will put more emphasis on alternative powertrains.

Lighter weight is significant because every 10% weight loss improves fuel economy by 3%-4%, said Pete Friedman, Ford manager of manufacturing research.

The annual Trends Report from the Environmental Protection Agency, released in December, shows the industry’s overall fuel economy improved by 11 m.p.g. from 1975 to 2013.

“We kill for 1% improvement,” said Matt Zaluzec, Ford technical leader for global materials and manufacturing research.

Ford has studied new metals, alloys and composites for 25 years. One of the early test beds was the Ford GT high-performance sports car in 2005.

Now the 2015 F-150 marks a much deeper real-world application. Ford sold more than 760,000 of the truck last year and is betting that cutting 700 pounds from it will ensure its long-term status as the nation’s best-selling truck.

The Lightweight Concept car was developed with the U.S. Department of Energy and Cosma International, a subsidiary of supplier Magna.

“There’s not a one-size-fits-all approach to lightweighting,” Zaluzec said. “The Lightweight Concept gives us the platform to explore the right mix of materials and applications for future vehicles.”

Ford is looking at oil pans and seat structures of carbon fiber, aluminum, diecast magnesium for some valves, and a combination such as an aluminum block with a cast-iron insert. Polycarbonates and laminates reduce the need for heavier glass.

A carbon-fiber composite seat structure would cost $55-$73 compared with $12 for a steel one, but would be 17% lighter. The other challenge is reducing manufacturing costs, said David Wagner, technical leader for vehicle design. A steel part is stamped every six seconds while the injection-molded seat can take a couple minutes.

“These are the kinds of technologies you’ll see creep into vehicles over the next few years,” Zaluzec said.

The next step is testing the full vehicle. Ford is building several prototype cars that engineers will put through the wringer.

“We will break these parts and we will learn,” Zaluzec said.

The work has a domino effect. If a car weighs less, it can reach greater speeds with a smaller engine. The Fusion concept features a 1-liter, 3-cylinder engine.

The strategy is to introduce lightweight solutions on specialty vehicles first, then on higher-end Lincolns, then mass-market Ford models.

In 2001, Ford Executive Chairman Bill Ford concluded climate change was real, and management resolved to make the company’s vehicles less detrimental to the environment, said Randy Visintainer, director of Ford Research and Innovation.

Ford also is working on a 10-year research project with Samsung to combine a lithium-ion battery with a 12-volt lead acid battery for use in vehicles with start-stop technology. The dual battery pack lets the lead acid battery crank the engine, then relies on the lithium-ion batteries to capture energy from braking to power the radio and air conditioning when the engine shuts off at a stop.

The challenge with a 12-volt lead acid battery is that in traffic, the battery controller will eventually tell the engine to not stop if it cannot guarantee it will start again, said Mike O’Sullivan, vice president of automotive battery systems for Samsung SDI North America. The lithium-ion battery ensures there is enough charge for the start-stop system to always work.

The long-term goal is a single lightweight lithium-ion battery that does it all — making the lead acid battery obsolete — perhaps in the next decade.

“We see this for mainstream high volume,” said Ted Miller, senior manager of Ford energy storage strategy and research.

While fuel economy improvements from start-stop systems do not register in EPA figures because of the way the government tests vehicles, automakers say they can improve economy as much as 10% in city driving with lots of stops.