Elon Musk / Tesla are doing a great job forwarding EV technology, however I just heard Elon claim that the D version of the model S can actually get more range, and it was implied it was because of the two drivetrains. (which he admits weights more than a single drivetrain). Why would his advisors allow him to claim this? Adding more weight to a car can never make it more efficient:- F = Force (the energy the battery needs to use) = mass of the car x the acceleration. Newton's second law of motion : F = ma . The vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration vector a of the object. Newton's laws of motion - Wikipedia, the free encyclopedia And before anyone says its because the second drive train can regenerate in addition to the first drive train, it still can never make up for the extra weight of the second drive train or you would be breaking the conservation of energy:- "In physics, the law of conservation of energy states that the total energy of an isolated system cannot change—it is said to be conserved over time. Energy can be neither created nor destroyed, but can change form, for instance chemical energy can be converted to kinetic energy in the explosion of a stick of dynamite. A consequence of the law of conservation of energy is that a perpetual motion machine of the first kind cannot exist. That is to say, no system without an external energy supply can deliver an unlimited amount of energy to its surroundings" Conservation of energy - Wikipedia, the free encyclopedia Think of it this way, if Elon Musk was correct then why not build a 100 drive train Lorry; that would have to be super efficient reneging all that power, even more than the force of moving all the mass of them 100 drive trains? Common sense tells you this cant be right. This was a difficult thread for me to word, I hope you get at least the point of the thread even if its not accurately worded? Maybe someone can explain my thoughts better than I can? No need to flame me, just state your point sensibly.