Every 200 miles add some distilled water,
"Bosch’s new WaterBoost system is geared to drivers accelerating quickly or driving on highways, where the additional injected water reduces fuel consumption up to 13 percent. The higher compression ratio in the engine also leads to a carbon reduction of up to four percent in WLTC (Worldwide harmonized Light vehicles Test Procedures), Bosch said in a press release.
Midsize cars will see the best WaterBoost fuel economy performance, with the system ideal for three- and four-cylinder downsized engines typical in new car models, the company said. The new water injection system can also make cars more powerful, especially by providing more kick to turbocharged engines, according to Bosch."