Originally Posted by deanshark

It'd be nice to know what year your car is so we don't have to search to find out. (1990) But anyway, I highly doubt you're getting 5 MPG. The only way to know how many MPG ya get is to fill the tank, go on your trip, and then fill your tank when you're back, then do the math for how many gallons you used for the miles ya went. Just going by the gauge, or even the computer in the newer models, isn't accurate at all. I'd say there's something wrong with your fuel gauge or the caps in the cluster. Very common problem on these cars.
Or you have a very bad leak in the fuel system just dumping it out, but you would smell that.

A little tidbit on mileage; When I bought my 93, I filled it and drove home over 300 miles all highway and filled it when I got home. I got 28 MPG. (In a 1993) Now most of the time I only drive about 2 miles a day. After tune-up, ECU, and everything else I did, I get about 14 MPG and believe it or not I'm happy with that. Most of the gas used goes to warming the car up or sitting at 2 lights and 2 stop signs. Ya gotta add that wasted gas into your mileage also. I laugh when people brag that they're getting 35-40 MPG. Ha. Hell, if ya go that way then my daughters Civic I get 70 MPG. (when I'm going down hill not touching the gas pedal)

Originally Posted by SwaysLS400

Deanshark, I am aware of the caps in the ECU of my ‘96 having the possibility of going bad but I’m honestly surprised you bring up the cluster I haven’t heard much about this, my fuel gauge stops at just above quarter tank, maybe you’d be able to weigh in on this?
Edit: Also figure I should’ve added this sooner but tachometer will stick around 1300RPM or so and with light throttle it will stay there but I hear the engine speed increase, however when I begin to open the car up, it releases the tach and it moves normally.