Wait, it makes no sense, but let's run our own mpg numbers. I'll start in L/100km as that's what I'm used to and I'll convert it at the end. My 19 year old VW golf Mk5 4*4 (hatchback) does 4.5L/100km or 43mpg on a highway. Now let's take Tesla's M3 real world tested 14.5kWh/100km (at 70mph on a motorway). Each liter of diesel contains 9.16kWh so this is essentially 1.58L/100km or 148mpg which is not bad at all for a 2+ ton vehicle. So where did the 68mpg value they supposedly multiply by 6.6 came from?