WASHINGTON—Regulators have sent the White House a proposal seeking to scale back Obama-era rules to combat climate change through tougher fuel-economy standards for cars and trucks. The Environmental Protection Agency and National Highway Traffic Safety Administration recently delivered the proposals to the Office of Management and Budget for review, one of the required steps before a federal rule is adopted.

This month, 33 cars will start the 101st Indianapolis 500 motor race. While each will sport a different color scheme, they’ll all share something in common. Every vehicle will be equipped with a turbocharger to boost engine performance.

DETROIT—As consumers clamor for better fuel economy, suppliers and automakers are trying to reclaim some of the lost thermal energy produced by a vehicle’s engine.