Transporter, that is the first I have heard of the Tatra 77a and the Cd figure is excellent so thanks for that interesting info.

Ramee has supplied the formula for estimating drag and I do not disagree with anything he has stated.
All other factors being equal, a reduction of the Cd by 10% results in a near 6% reduction in fuel consumption at a steady 110kph.

I did appreciate the effort Skoda put into producing a larger and much lighter car with very efficient drivetrains, but I stand by my initial statement that Skoda should have reduced the Cd on the new Octavia as VW did with the Golf wagon.

After all the TV Mythbusters team unintentionally managed to reduce the Cd of a Ford Fusion by more than 20% just by covering it with clay and putting large golf ball type dimples into the clay.
You can usually shoot cannon balls through the holes in their methodology with regards to car fuel consumption myths but that one was particularly elegant and well executed.