fuel indicator reads half after doors lock
 

hey every one im sorry if this is a dead horse... BUT i did a search and can not find my exact problem.
so it seems like my fuel indicator reads normal when i first fill up but if my indicator is right then my blazer is only getting about 9 MPG bc at 180 miles its empty and the low fuel light is on. Also when i close the door and lock it after about 30 to 45 seconds later my fuel indicator and my oil pressure indicator jump to about 1/2, and wont go back down until the key is inserted in to the ignition. any one else have this problem or might know where to start??? thank you for your guys time sorry its so long.

mileage should be calculated by filling tank, driving until low, filling again.... miles since first fill divided by gallons used to fill the second time is mpg. my gauges do the same when i lock the doors also (with key out)

i under stand how to calculate mileage, my problem is, well at least i hope, the indicator is wrong.

the indicator has nothing to do with mpg... only tells you how much fuel is in the tank. just check what it says next time you fill up, if it says E and you only put 8 gallons in then the indicator is wrong....the sender units are know for failing after time...