I have fitted over size tyres to my gen2 Prius. The tyres are Hankook kinergy eco K425 205/55/16. These tyres have a tmp (turns per mile) of 831 against the OEM tyres 851 a difference of 2.4%. Apart from helping to correct the optimistic speedo it will make the odo under read my mileage by 2.4% witch means I believe that when I calculate my fuel consumption I must add this 2.4% to my total miles for each tank. Strangely if I do this my calculated figures come out at virtually the same as the MFD. Am I doing this correctly or am I missing something.