Has anyone else noticed that the HCH gets really high MPG numbers right after a fillup, then goes DOWN from there? Or is it just the way I fillup?

I ask because I usually fillup at Sams' Club, the closest of which is about 6 miles from my home, and others I use are 10-12 miles from home. So immediately after filling up, I always get some good "high mileage conducive" city street driving at 35-45 miles per hour before getting home.

My MPG on the FCD when I get home is usually ALWAYS at least 65 MPG, sometimes has been as high as 73 MPG for that first 5-10 miles immediately following the fillup, then after that it starts to quickly drop. Within 30-40 miles I am usually back down in the mid-50s, which is where my tanks lately have been ending up.

Does anyone else see this in their HCH? Or is it just the mechanics of my fillup process that is causing this, meaning the way I get to drive it for high MPG right after filling up?

I know that in non-hybrid cars, car makers have always intentionally caused the first half of the tank to show "higher MPG" to let new buyers think they are getting such a great car (started I think in the 1960s) and I wonder if a little bit of that has been incorporated into the HCH by tradition?

Anyone have any similar experience or ideas? Just curious !!!