http://www.nytimes.com/2016/09/30/a...gines-more-efficient-just-add-water.html?_r=0

New York Times article from September 30: BMW is using Bosch's Water Boost system in the M4 GTS. The system uses water injection (distilled water) to cool the fuel-air mixture, reduces knocking potential and makes the turbocharged engine more fuel efficient. There are some drswbacks to this, one being that you have to keep adding water to a tank. But if this works well on the M4, why not add it across the mode line, from the 3 series cars to the 7 series and the SUVS?