1986 Chevy S-10 Blazer gas gauge not working

If this vehicle has a 16 gallon tank it seems that the fuel gauge is working as well as should be expected.

Thatā€™s 4.5 miles per gallon. Obviously not correct.

Car has 20 gal tank. With 235 instead of 205, odometer is off about .1 per miles driven.
Planning on trying tune up route now that I found out how to get fuel filter out from
Power steer pump.