Do I need a fuel sending unit?
 

This morning, I noticed that my fuel gauge was reading 7/8 full after I'd already driven about 180 miles. My DIC confirmed that I'd gone that far, but claimed that I had 330 miles of fuel range left. When I stopped the car last night it was showing a lower level on the fuel gauge and calculated a range of 250 miles. I topped up the car anyway because I am driving 300 miles by tomorrow morning, and it took 6.2 gallons. DIC accurately calculated 26 MPG. Given that the only calculations affected are based on faulty data on how full the tank is, I believe the sender is failing. I am not showing a check engine light.

Sounds normal to me. Fuel gauge is slow since I bought it new, I assume its all HHRs.
I go for a two hour drive, the gauge hardly moves, then after parking for a few hours it drops to the proper amount.

Where i park mine overnight it leans towards the passenger side. If it leans that way it always reads way lower than when i shut it off. If i back in and it leans towards the drivers side it shows more full. Idk just an fyi