Is It Just Me?

Or has anyone else noticed that their gas tanks seem to hold more gas all of a sudden?
No - really. I'm not crazy.
My significant other has noticed the same thing.
When my fuel gauge is right on E (yes, I know it has a reserve), I have generally put about 13.5 gallons of gas in. This was true for all the years I have owned the car (5) - except for this year. This last year, I am able to get something like 14.5 - and once, even 15 into this tank!
How?
Would anyone care to hazard a guess?
Oh - no, I am NOT getting any more miles to a tank of gas............ you would think I would as I am obviously putting more gas into the car - but I'm not. (Yes, its been tuned and yes I have double platinums in there and yes I have had the oil changed.)
I'm sure this is a phenomena that happens to some cars in particular and not others. And it is obviously some phenomena of which neither I nor my significant other are aware.
Any ideas?
Or maybe............could it really be just us?