I'm sure many of you hypermiles will not be that impressed, but I got 74 mpg the other day on my way home. Yeah!!! I was excited. I ususally average around 53 mpg. I purchased my Insight to travel in the carpool lane so my speed is usually in the 60-80 mph which doesnt get the highest mpg. The other day I was really late going home so I missed the carpool hours and having very high winds on the San Mateo bridge and drafting with the trucks I did mangage to get 74. My old high was 68
To be drafting you have to be very close to the rear of a big semi rig. This reduces the wind resistance allowing your vehicle to gain fuel mileage. You have to be so close that if the vehicle in front of you reduces speed suddenly, you would hit them.
But if you are at a legal safe distance then you aren't drafting and don't get the mileage results.