Autobahn + Tesla car = pure dream.
The batteries will be gone in minutes though.
Obviously you can go faster on the derestricted sections of Autobahn but you REALLY need to concentrate and plan well ahead at >150mph and that drinks fossil fuels too not just batteries.
Edit: A bit of extrapolation from the ranges on seems to show at a first aproximation you could do a little less than 110 miles at 120mph. Based on the datapoints in the parent's link a drop of 5mph gains you a range of about 8%.
They had to travel from one city to another (using autobahns) and arriving as fast as they legally can and they will take cost, time and comfort considerations.
I won't spoil which one wins just in case you find the video =)
It's all about the power - at high speeds that massive V8 engine was still very relaxed, at 200km/h it was doing 3500rpm, while the 1.6 diesel hits that at around 140km/h, so anything above that speed is super inefficient.
True, but gearing and power are two sides of the same coin. You can't have tall gears if the engine doesn't have enough power to move the vehicle or sustain speeds on the highway.
Autobahn + Tesla car + dead inexperienced high-speed driver = pure dream