I've read about this before and today it happened to me.
After refueling, a normal refuel... pump clicked off and then I just pumped a little more to round off the cents.
Get back in the car to continue back home and the instantanuous MPG is way higher than before. It was showing between 125-140 while holding 50 miles per hour on a level road. It's never done that before. I was enjoying it! Woo Hooo!
But it was short lived, after about 7 miles, everything returned to normal.
What is going on here? MPG mis-calculation? Lots of fuel vapors being recovered from the refuel?
Thinking about topping off the tank to see if it will happen again, but don't want to waste the time stopping.
Regards,