I believe their has been an on going governmental / auto manufacturer / oil company conspiracy, to control the market, drive consumption, in order to fund the government through controlled amounts of consumption I.E. Revenue in taxes.
Their have been all kinds of stories about this, some believable, some not,
Here is a link to snopes related to the pouge carberator story that started it all.
Here is a link to a diesel ford tempo from the 80's my brother owned one of these and you could get 50 miles to the gallon on the hyway.
The New diesel ford focus gets over 50 MPG conventional, not sold here.
If this technology was available in the mid 80's, WTF is going on now, Why can't the manufacturers sell these gas / diesel vehicals here, why are we off on to a battery operated car that will go 40 miles and cost $42,000 dollars.
Why does my truck get 12.4 MPG,