2005 Ford GT: Runnin' On (actually, below) Empty

Aw man, I hate that. My wife gets antsy at 1/4 tank. More annoying to keep driving with her whining than to pull over way too soon...

I can attest that my car's guage is right on target. With an 11 gal tank, I managed to get 360ish miles once (all highway, 93 octane). I confirmed it when the engine began backfiring as I pulled into the station. The tank then took 10.989 gallons. Talk about close!
 
My truck is nowhere near as reliable. I've never tested it's limits, though.

Not sure where your fuel pump is located, but on many cars it is in the gas tank, and it uses the gas to cool it.
So many mfgs make the gas gauges pessimistic to prevent damage to the fuel pump by people running it low on gas.
Maybe something to think about.

I'm pretty sure my mom's Prius will let you know you're "empty" when you still have 3 gallons left, or about 150 miles. Often we'll have it down to 1 bar on the gauge and then fill up for 7-8 gal.

I'm a bit paranoid with gas myself, haha. My car, an '05 Nissan Altima has a 20 gallon tank (pretty big for a sedan, but the car is a bit of a boat too) and the fuel light came on once and when I refueled it only took about 17-18 gallons if I'm not mistaken. I usually try to fill it up when I hit the quarter full mark or so.
 
I think the manufacturers are just giving their customers a lot of wiggle room when it comes to refueling their vehicles.
 
Although doesn't a lot of dirt or whatever gather up towards the bottom of the fuel tank? I've heard that's why it's better to refuel when you hit the quarter full mark. Perhaps the manufacturers have their fuel lights come on so early so that people will refuel before some of that gunk gets into the actual engine and therefore harm its long-term reliability?

I'm pretty sure the 5th gen Accord has the mother of all "Cry Uncle" gas guages. If you stop and put gas in it when it's on E, it taks 12 gallons. But it has a 17 Gallon Tank! It's so frustrating- the car could be a range champ, but like Karl said, it takes lots of guts... That, and it starts not wanting to start when it has <3 gallons in it. Most I've ever filled up with was 16 gallons (the needle was a good 1/3 inch bellow E). On the other hand, my dads Suburban is actually pretty close to accurate. I ran it down to E once, and put ~39 gallons of gas in it. 40 gallon tank. And one gallon will not get you very far in a '90's 4x4 Suburban.

I used to push the limits until I ran out of gas one day... now I don't use the gas gauge anymore, but use the trip odometer since I rarely use it for anything else. My gas gauge is so wonky that I have had the low fuel light come on at below 200 miles before and sometimes above 250 miles. So now I just know that when I reach around 250 miles it is time to fill up. This usually results in about 14-15 gallons for around 16 MPG (if I have done a lot of highway driving I get almost 20 MPG but I still fill up at 250 miles). I have an 18 gallon tank, so I could go a bit further. It just helps to keep things simple...

i use the odometer trick too. although for a different reason. My fist vehicle was a 1973 Dodge Pickup. The guage was inoperable when I bought it. So i carried a 5 gal. lawn mower can in the bed. After I ran out of gas a few times I could reliable go off of the odometer. (no trip) I had to keep everything in a notebook. But it got 12 mpg with a 32 gallon tank. I only miscalculated once and had to walk a mile to fill my can. I guess I was lucky.

desmolicious-
My old Alfa Romeo Spider had not one, not two, but three fuel pumps- one in tank, the main pump above the rear diff, and the injection pump in the engine bay. The aft two were gas cooled, and the front one oil cooled via a captive supply and filter. Gotta love the Italian cars...

Edmunds should test the limits of a few of their fleet vehicles to see how far they can go after the light comes on.

As someone with a couple classic cars that never have working fuel gauges, I simply have a running distrust for fuel gauges and chicken out too early.
 
Besides, I never know when I'm going to be driving somewhere (in my modern cars) without the luxury of time for a fill-up. So better to fill-up when I know I have the time than run the chance that I won't have the time later.

I never push my luck with the fuel gauge.
 
I fill up once a week when we do our shopping, unless we really don't need it. I'm usually right at a half tank.

That gauge is very conservative if it was that far past E, and you still had 2.5 gallons left. In my Z06, E really means empty. I've had it down to 0.5 gallons left, and it was pinned on E.

The gas gauge in my Focus is very conservative too. Supposed to be a 14 gallon tank, but I've never put more than 12 gallons into it, after the fuel light was on for 15 miles. My goal is to hit 400 miles per tank, but once the fuel light comes on, I'll typically fill up asap.