84-88 gas gauge

alright, i have been driving my truck the past couple days and the gas gauge is way out of wack. the guy who did the gas tank work said its a good sending unit, everything is clean. he put 2.5 gallons in to run it, make sure all was well with the tank. well i put 20 dollars in, at 3.159 a gallon thats ~6.3 gallons. The tank is 13.7 gallons. So in total I have put in roughly....say 8 gallons. A bit over half a tank. (~6.75 gallons)I drove home from the gas station, back to campus (5 miles each way) and then to the parts store (5 miles round trip). Today I went to campus and back (10 miles) so total like 25 miles, call it 30 to be safe. Now I should get 17-20 in the city i would think..

my gas gauge read over half a tank at first, and right at a little later. on the way to the parts store and all it kept dropping. right now it sits at about a 1/4 tank. so its like i only have like 3 gallons left. does that not seem really low? 3 gallons should take me 45 miles or more....

if it sounds right, ill live with it, i just dont want to run out of gas in traffic and have to leave it in the way of the morons driving around here.

My gas gauge typically drops very slowly for the first half tank. Like 200 miles plus on half a tank. Then the second half will be between 100 and 150 miles depending on how much town driving I do. I also have a 12 gallon tank.

Aside from that, I have no useful input.

my mustang does that too, maybe its how it should be, well see how it drops from here.

that sounds about right for my 86. like seth said the first half of the gauge is almost the whole tank

i put in 4 gallons and got all of 60 miles. so...15mpg, something is wrong.

anyone know what ohm the stock gauges are for 85?