I drove a '76 Toyota pickup for 2 years without a gas gauge, and never ran out of gas.
The very first thing I would do is check my MPG.........fill it up, drive for 100 miles or so, and fill it up again - miles driven divided by gallons used = MPG!! Figure that out and at least you can drive it with some piece of mind.
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The only terrorists I fear reside in Washington, DC.
'03 TJ - 31x10 Trailcutter M/T's, 9000# Winch, Hi-Lift Jack, TopFive roof rack, only vehicle I own, takes me everywhere