Scientists are exploring a surprisingly simple way to clean up diesel engines: adding tiny droplets of water to the fuel.

We may receive a commission on purchases made from links. The engine bay under the hood is one of the dirtiest parts of a daily-driven car. But it's also one of the most neglected places to clean.

The diesel engine has undergone a significant evolution over the past two decades. Most of these changes were designed to reduce emissions and air pollution, but once early generation emission goals ...