The free tool requires manual input of meter readings, providing graphics for the specific consumption per day. It may also correlate two meters or transform odometer and fuel amounts into l/100 km or MPG.
You may enter the meter reading(s) whenever you want, the server based software calculates the specific consumption. Your code encrypts your data, so the operator of the site has no access. By October 2016 SSL will be added to make it even safer.