Funny/entertaining topic.
As many indicated, Range is determined by many factors - Towing/load, going up or down hills, temperature, city driving, city & HWY driving, etc.etc.etc.etc.
The computed range indicator never matches the reality based on the details of a given drive. Unless your drive details are consistent. Then the trip computer is +/- a couple of MPGs.
Reset the trip computer after every fillup.
If you don't and your drive details are diff. the trip computer calculates based on the residual memory from the last drive's details.
My range to empty driving the same route is around 550 miles. When I tow my trailer up and down the mountains from PHX to UT, then it drops to 400 miles or so. It takes couple of resets to get it back to "normal, no tow" range when I am not towing.
Low fuel light is a better gauge (should never let it get to that point).
Low light can come on with 4, 6, or 8 remaining gallons depending on the vehicle's pre-set threshold from the factory.
my 2 cents!