Hmmm. At the time the warning came on I was averaging 23 MPG, so if my tank only took 12 gals of gas, I should've had over 60 mi left to travel instead of the warning of only 37 miles. Just trying to understand how much of a fudge factor the warning is really giving, LOL!
I think the miles till empty is effected by your speed also. When I fill up and then drive 80 on the interstate, yes that is the legal limit here, it does not correlate at all. I have not done a study but it is quite obvious on a 120 mile interstate only trip.
P.S. I have never seen the warning light, in this country when gas stations may be 50 apart you don't want to have anywhere near an empty tank. When it hits a quarter it is time to fill up.