I was reading about this and assumed it only worked on hybrids like the Prius. I finally googled it and it supposedly works on all cars. Here's the theory as a simple example: if you're getting 30 mpg getting up to speed, say 60 mph, take your foot off the pedal and glide back down to 40 mph. With the foot off the pedal you're getting infinite mpg because you're using no fuel, effectively doubling the distance traveled per fuel consumed. If you've driven an equal amount of time pulsing and gliding, the average works out as 60 mpg. The average is greater than what could be achieved just driving at a steady speed of say, 50 mph. Any long term tests with your TDI?