Actually there s a more serious point to be made here Most of the physics was worked out long before the first practical car the Victorians invented most of the mechanisms that we still rely on in the most technologically advanced machines today Most progress has been in terms of a miniaturisation think of the cogs cams and levers in a Mini DV camera for example and b in machining precision The petrol powered car engine is now reaching the order of about 37 efficiency approaching the theoretical limit having started out at a much lower figure Many ingenious solutions contributed to this but at every evolutionary step what was possible within the constraints of cost and materials as well as theory had to be applied As engines have become more and more productionised going through many generations of evolution the use of e g fuel injection over a simple carburetor becomes practical as well as hundreds of other small improvements But the main reason that a production engine today produces more bhp per ton than the racing engines of 40 50 years ago is that precise machining is now routine rather than the province of specialist hand builders We have CAD and CNC to thank for that But no matter how much this process might continue in future and it will though improvements will be to reliability and extending service intervals rather than basic efficiency as long as we stick with petrol as a fuel and internal combustion as a way to extract its energy we are asymptotically approaching the 40 limit and the only way beyond it is to build our cars around a radically different energy equation which is where research into electric cars et al comes in If an efficient process that can convert chemical directly to electrical energy is found the Carnot cycle doesn t apply and much more efficient cars will come about In terms of better gas mileage etc improvements can still be made by making cars that are lighter less rolling resistance more aerodynamic etc so they require less power to propel them The IC engine is stuck at 40 efficincy no matter what though