Was it Babe Ruth, someone asked him: "Where do want to be buried?". To which he replied: "Surprise me."
My Gen II from 2008 (European version with 195/55R16 tyres) gets in summer consistently 54mpg (=4.3 l / 100 km). Best so far for more than 70 miles: 76mpg for a distance of 72 miles (3.1 l/100 km for 116km). On longer distances in real traffic I might a consumption of 58mpg for a distance of 621 miles (4.0 l/100 km for 1000km). Screenshots from European version: 29lkm_20km by Pale Fox posted Nov 6, 2015 at 10:33 PM 40lkm_1000km by Pale Fox posted Nov 6, 2015 at 10:30 PM
As of today (November '15), I agree with Mendel - The Plug-in Gen III has the highest MPG, even if it is never plugged in and used as a hybrid. Once the Gen IV is in the wild, that answer may change
That was just the first of many: Another World Record 1,460 miles/tank | PriusChat 1,562 miles, New World Record with a single tank | PriusChat New World Record - 1619 miles per tank | PriusChat New World Record - 1680 miles per tank | PriusChat New World Record Challenge: over 50km/L(117mpg) tank | PriusChat That final one went 1889.4miles (over 3000 kilometers), with a final result of 118.6 mpg.