Mines like clockwork,8 gals remaining when fuel light comes on,104 miles to go.
When full divide miles driven by gallons pumped.
I have OEM navigation and the DTE is as conservative as the warning light.
The DTE estimation sucks,the MPG is usually right on.
I really liked my last Chevy truck had a gallons consumed function that was dead on when comparing to fill ups.If it said you used 23.2 gals,it took 23.2 gals to fill it.