I decided to add a bit of aero to my VW Jetta Diesel. I have been able to get 55mpg all summer. The car does not lend itself to instrumentation that can measure fuel economy. No computer to tap into.
Here is what I was able to come up with.
The vehicle is almost always driven with the trunk full so getting into the trunk is important. I raised the trunk and used some cardboad boxes to shim the top piece of 8mm thick coroplast to the expected angle of 15 deg at the back of it.
The sides were made from 4 mm coroplast. I heated and folded the joining surfaces so that it would add strength and stability. The sides taper in. I under-lapped the two pieces that make each side and to add taper.
The other aero aids are the piece of unbacked formica shaped in front of the grill, a hood splitter and an extension on the stock under bumper spoiler.
Last year my goal was 50 mpg since I have seen 57 mpg twice in a row I am hoping for 58.