I can believe it. In a Ford F-150 pick-up with a 4.9L in-line 6, 5 speed manual, driving very carefully on a motorway trip, being careful to keep it at 60mph I was able to achieve 20mpg when my normal milage has consistantly been 12 - 13 mpg. I was able to duplicate the same thing on several occasions, as long as I can maintain the 60mph, usually I end up around 70mph and blow the milage down to the 12mpg range.
Drafting large lorrys/trucks, or tractor-trailers is also another way to increase the milage. Just don't ****-off the other driver, sometimes they don't take to kindly to the sport of drafting. They confuse it with tailgateing. Hmmmmmm, I wonder why!
