Have had this 1995 Z28 about 9 mo. Was told by previous owner not to let it get below 1/4 or it will run out of gas.
Just had the pump/sending unit replaced, threw a can of gas in the back, and drove it till the gauge needle was covering the top of the E. Filled it up and it took 17.675 gal. The owners manual says it has a 15.5 gal. tank. Every where else I look says 15.5 gal. tank.
Is there a secret 18 gal tank option?

 

The same steel tank was used in the 3rd and 4th Gens from 1982 up to 1998. All listed as 15.5 gallons. In 1999 they went to plastic and managed to squeeze a 16.8 gallon tank in the same space.

Maybe try a different station, with a current weights & measures certification sticker on the pump.

 

I’m with Fred — the most likely cause here is a faulty or miscalibrated meter on the pump.