A German aeromodded his 2006 Passat wagon and improved fuel economy by 20-25%
 

Apparently, he put everything back and sold it but mentioned it in other videos, so he shared pictures and data that he had.

He bought LLR tires, moon discs and spacers because his rims were too wide, lowering springs, removed his roof rack, blocked off grills and vents on the inside with aluminum plates and tape.

He said that his fuel economy improved 20% in-town and 25% on ze Autobahn. https://www.youtube.com/watch?v=Cipry8uV5QY YouTube recommended this video, but I am just going to read the first three comments and move on: https://www.youtube.com/watch?v=gizUuHuCxy4