The recently-announced 53 percent boost in fuel economy requirements by 2025 is unlikely to prompt a dramatic increase in production of electric cars and hybrids, which are only a fraction of the U.S. sales market. Automakers will still rely heavily on gasoline engines. Experts say the industry will accelerate development of cleaner burning gas engines, enhanced transmission systems, lighter materials, and more aerodynamic designs. The auto industry has made good-faith efforts so far to focus on fuel-saving improvements in a shift toward production of small cars to meet consumer demand and new government mandates in an era of high gas prices.