I get around 17-18mpg avg in my 50i with Dinan stage 1...works out to about 375 miles per avg tank (max of 425). Overall it is much better than the M I had previously which got around 13mpg on a good day and had a range of a little over 200 miles per tank.
2011 Nissan GTR Red/black - HP Logic tune/midpipe - "Lightning"
2012 BMW X5 50i M-sport Dinan S1 Space gray/black - "Thunder"
2012 BMW 550i M-sport Jet black/black - "Black Cloud"
Gone but not forgotten: '12 X5M, '07 AM SuperVantage, '05 Boxster S, '01 BMW M3,...