When was the last time someone bought a new car with magnetos and a low pressure fuel injection system let alone a carburettor?
There have been huge gains in economy in autos (ild hate to be running a 308 like my first car now, would cost a fortune) but unless we change our thinking and use electronic timing, high compression and reduction drives not much is transferable to aviation, and reductions could never work that's what turbines never took off....