let's see.....

My Opel Zafira car has an diesel engine, 4 cylinders.

And I get something like 58mpg out of it (6.5 liter per 100 km).

It has enough power ( more than 100 horse power) to haul 350 bottles of Sancerre back home, at 81milles per hour (max speed on french highways)

So what more should I need ??

a much better mpg is possible with some newer cars.