Ok, so I've been having this argument with a friend of mine. If my vehicle is on a straight, flat piece of the world, what would be its potential energy? I say it would be 'x' . Any value larger than zero. Him, on the other side, say it would be zero. His reasoning for that answer is that Potential Energy = m (mass) x h (height) x g (gravity). In that equation, he is correct. I do agree with that. But to me, that equation would be for gravitational potential energy. My reasoning for it being larger than zero potential energy would be because of the fuel stored in the tank. And also the fact that you have electrical potential energy stored in the battery. The way I understand it is that the total energy before a given moment in time, must equal the total energy plus the losses after that moment in time. (Given the law of conservation of energy). And also, as far as I understand, the total potential energy of a system is the sum of all possible potential energies. Please can someone explain where I am wrong? And I say that I am wrong is because I have been proven to be wrong before. Thanks.