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I am stumped on something right now. I am only getting around 190200 miles to a tank, yet when I fill up I am only pumping 1011 gallons of gas. And my fuel gauge is reading empty here for sure. I understand that the tank is 16.9 gallons,

the fu8el guage sending units are notorious for showing empty before the tank actually is. figure out your MPG and multiply by 15. this is your crusing range. reset you trip odometer every time you fill up. as mentioned, the low fuel light should come on around 23 gallons left.
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I do have 18" wheels and the tires are 245/40/18, so is it possible that the miles are that far off since the wheel/tire diameter is larger than the OEM 15" steelies?

yes, this will DECREASE your MPG and your miles per tank. your car is driving faster than the what speedo says and toy are driving farther than your odo says.
but the above solution, MPG times 15 with resetting the trip meter, will still work.
FYI:
your tires are 25.71 inches in diameter. this is 1 inch larger than the stock tire 24.68" diameter. or 4% larger.
so at 60 mph you are actually going 62.5 mph. and when
the trip meter shows 100 miles you have actually traveled 104 miles.
not a huge error, but still an error.