Usable Fuel Capacity, how much have you used before running out?

[spearfish25]

The other day I was driving to work and my trip computer was flashing '35' miles left to empty. There were two dots remaining on the fuel gauge. As I kept driving the 'miles to empty' value worked its way down to about '18' and then the gauge dots went down to one. At this point the fuel computer stopped reading miles left to empty and just put dashes across the readout.

I freaked out despite knowing that one dot on the fuel gauge corresponds to over a gallon in the tank. However, it brought up an interesting question.

What is the USABLE fuel quantity in our 19 gallon tanks? When I filled up that day, I got 18 gallons in the tank. Today in a similar situation I got 17.5 gallons in the tank.

So, what is the most gas you've put in your tank (ie how close to 19 gallons have you come without having the engine die on you)? Anyone tempted fate and lost, running out of gas? How much did you put in when you filled up then?


Addendum (to clarify the questions):

Originally Posted by Chupacabra

I thought out tank had an 18gallon capacity. But if its 19, why does the screen go to the dots?

Nope, it's 19 gal. See the manual clipping from below.

With 16 LEDs for the gauge, each dot represents 1.12 gallons. I've found it's pretty close to dead-on. However, knowing you have 1 gallon left in the tank doesn't mean you have one USABLE gallon left. Depending on the tank shape and pickup, you may not be able to get all of that remaining fuel out. Hence my questions (I should have explained better).