Distance to Empty Reading With Oversize Tires Using Gap IID Tool
 

Has anyone used their Gap IID tool to obtain an accurate Distance to Empty reading on the instrument panel after installing oversize tires? If so, what settings have you used? I have a 2013 LR4 w/ HD package, running 275/65 R18 tires (BFG KO2) and 2.5" John Rod Lift Extenders. I've used the Gap IID tool to modify the IPC Instrument Pack after reading the forums, so my speedometer looks accurate when I drive using a GPS device to track speed. However, my fuel gauge seems off. The max Distance to Empty with a full tank of gas usually displays about 290 miles. I've driven several times now to Distance to Empty of 0 and my low fuel warning light comes on, yet when I refuel, there's still about 6-7 gallons remaining in the tank (I'm only refilling about 16-17 gallons of gas). My current settings in Gap IID for IPC-Instrument Pack are:

Tire Aspect Ratio: 65%
Tire Size (rolling circumference): 2365mm (that's the largest option you can select)
Tire width: 275mm
Trip Fuel Eco Adjust: 0%
Wheel Rim Diameter: 18 inch
Tyre ROlling Radius: 394-275/65R18
Tyre Size MSB-IPC: 30

Does adjusting Trip Fuel Eco Adjust make any difference? Is there a way to get a more accurate calculation? I've tried resetting my trip odometers and nothing appears to be wrong with the fuel sender or fuel gauges (no error codes and fuel level gauge doesn't jump around like some forum members have mentioned).