What percentage of MPG increase can I expect?
Since I am not familiar with your specific car, engine type, maintenance record, driving styles, etc., it is challenging for me to give a prediction in your exact case. I encourage you to view testimonials of people using this technology to get an idea of the ranges that other people are getting:
http://www.runautowithwater.com/#testimonials
Alan
Mechanical Support
http://www.runautowithwater.com