80+ mpg... so what
Engines these days are more than capable of achieving this sort of figure... but the consumer and political need to make cars safer and have more gadgets to make them safer and more fun... has added huge amounts of weight to your average vehicle.
Take a modern fuel efficient engine of say 1.6 or 1.8lts and stick it in a car from 20-30 yrs ago that had the same sized engine... and you'll see just what a difference it makes.
Like the guy who dropped a 2lt Honda engine into an old Ford and was getting 50 mpg and upwards... the car was 200kg's lighter.
I know some will harp on about crash cells and safety features... but cars can be built strong and safe with lighter materials at not much extra cost these days... Some are already using plastics on certain body panels... and still these cars are heavy lumbering beasts that can barely match the MPG's of cars from 20yrs ago.
Here's another example... I owned a 1990 Ford Sierra 1.8lx and on a run it would do 39mpg that's 70-80 mph for 400 miles.
I now drive an 07 Mazda 3 1.8 TS2 and get 40 mpg on a run at the same average speeds.
I know for a fact the Ford engine in my old sierra was not a very efficient one, wasn't even fuel injected... The difference is in the weights of the cars... and the Mazda 3 is supposed to be the smaller of the two.