I'm driving down the left lane of a three lane highway going 40 mph with a car in front of me that I'm drafting in behind. There is someone in the right lane next to me going the exact same speed. The car in front of me stops to turn; I slow down to 30 MPH for two seconds and swerve into the center lane and re-accelerate to 40 MPH. Clearly, I am able to benefit from this as I spent less energy over the previous quarter mile because I drafted behind, despite giving up 29 feet of distance to the guy in the right lane in that two second period.
