Gas Gauge showing Full when tank is not - Why?

[Woodenfish]

with Peter 99% .... On the Lubricity thing, I don't think the Fuel pump gets any " lubricity " from the Gas. ... It does Require the gas to help cool it ..... JMHO .... Mike

The electric fuel pump does not get cooled by the gasoline. The motor does not run hot nor does the pump generate any significant amount of heat. Gasoline and/or water are not lubricants. Diesel fuel is different. I don’t know where you all heard this but that certainly is unique news to me but posting smileys in a debate does not make it true. When the gasoline level runs out the fuel pump is shut off. EFI engines have a fuel rail pressure sensor and a pressure valve. The ignition switch has to be recycled to get the pump to activate again. It is calibrated to achieve a certain amount of pressure in a given amount of time. The electric fuel pump motor is very robust and capable of much higher fuel pressure than required and much more volume than needed. The EFI fuel pump sits inside the fuel tank in a plastic bucket to maintain a volume of gasoline around it to prevent cavitation and loss of pressure during driving creating the fuel to slosh around where it might not be reached by the pump inlet. That bucket is there to help the pump maintain its prime. This bucket also happens to be a good place to mount a fuel sending unit and manufacturers call this assembly a module.

[Jesster72]

I don't necessarily think the gas gauge is that terribly inaccurate! All you have to do is visualize two invisible bars at the top and one invisible bar at the bottom for a total of twelve bars. I find by doing that I generally get about 15 miles or so per bar, top bar to bottom bar. The top visible bar disappears after about 45 miles and when the gas light comes on there are two bars, one visible and one invisible, of gas left for about 30 more miles. And then there's still some left that you don't want to use up or you'll be stranded or suffer the consequences Peter warns about!

Two things....
Idaho, I hope you don't mind, but I laughed really hard at your post. The invisible bars on the guage. Gold. Thank you. Makes me glad I stopped in to read this one, I figured there would be a bunch of (good) info about using the trip meter and filling the tank full up each time, I almost skipped by this one.

the other thing (#2 if you will) is agreement about milage varying. Interstate travel sucks the gas, and I stop about every 150 miles, more for me, since I'm ready for a break about that time, and a fuel stop just fits then. 2 lanes I seem to be able to wrangle with that magic 200 mile mark without getting the low fuel warning.

Thanks to all, even the long-winded Peter, I try to learn from everything I read here, well, almost everything.