Honda will be hawking its new 80-mile-per-gallon “Insight” in showrooms across the U.S. by the end of this year, the company announced yesterday. The two-seat coupe will be the world’s most fuel-efficient, gas-powered, mass-produced vehicle. The Insight, which will be priced below $20,000 in the U.S., has a three-cylinder gasoline engine assisted by an electric motor, and lightweight plastic and aluminum body panels. Toyota was the first company to sell a hybrid gasoline-electric car — the Prius went on sale in Japan in 1997 — but it won’t hit the U.S. and European markets until next year.