Rep Power: 0

My gas gauge is going down too fast, but the display is still reporting reasonable mileage.

I had an oil change where the maintenance signal had to be reset recently, but otherwise nothing has changed.

My first 80 miles ~42mpg are reported, but the gauge is only around 5/8 after a fill-up.

If somebody stole gas out of my car or there was a leak in the gas line, would that affect the display?

 
Rep Power: 125

No. Very unlikely someone is stealing gas, though.

Honda fuel gauges aren’t super accurate anyway. They aren’t linear so you’ll notice no drop until almost 100 miles, then it’ll drop down to about 2/3. Depending on the range you’re getting, I wouldn’t worry about it.

 
Rep Power: 366

suspect the gauge first. also, gas pump sometimes will stop before it is filled.