Ok, this is weird and i hope someone can shed some light on it.

I filled up my tank on Sunday evening, about 13.5 gallons. the readout on the "miles to Empty" was about 420 or so, I don't quite remember. But i reset the tripometer as i always do on fill up.

So Monday we did some short trips about 20-30 miles or so, maybe a little more or less and Tuesday my wife took the MMH to work, about 20 miles total. So i was in the car today and the tripometer was at 77 miles and the miles to empty read about 350 something which made sense because we were a little above 3/4 of a tank and you could obviously see that the fuel gague was below full and closer to empty. I usually get about 100 miles for each quarter tank (just a visual from the fuel gague).

Well, i went to the store and when i got back in and started it up, the tank was now back up to full, no lie, right on the full line, and the MTE read 402!

How could i have more gas in the tank now?? I shut down and restarted and the same information was showing.

Now, i know the above information is vague on where my mileage actually was because i usually do not look at it when at a full tank, but id know for sure that the fuel gague was almost at 3/4 tank because of how far i had travelled (77 miles) and now it is at full.

I was on level ground when i checked all of this.
Any ideas what happened?!?