No offense but this fairy tale ideal that the city centric bunch always comes up with completely ignores that so many items people want or use in everyday life won't be made in their own city let alone one near by. Throw in the higher costs of living in the city both financial, mentally, and physical, and I still have a hard time justifying it.

Improving efficiency helps everyone because there is not going to be any overnight and likely within one generation shift to another lifestyle. You will never have all the jobs needed within a city to support all the people who live there. As in, your electronics, your food, and many other items, will be produced elsewhere and have to be sent there. The only things cities can self support usually are services.

Cars became popular not because fuel is cheap, they became popular because they represent the freedom to go where you want when you want. You are not restricted to some bus or train line whose routes and times are determined by a government agency.

So efficiency of the internal combustion engines is a needed move simply for the reason that not everyone can be put on the same schedule to change to the next means of individual travel.