In driving to work yesterday I left the house with ~450 miles on the clock and about a 45 mile trip to work (I usually fill around 500 miles). I had 4 bands on the fuel meter. A couple miles from work, while on a bridge in bumper to bumper traffic, the light came on and I had no bands

Over the next couple of miles poking along, the light went out and 3 bands reappeared. I was able to drive at least 10-15 miles with 3 bands to get gas. This has happened before, but dropped only to 1 band last time.

What's the deal? How can a deal with the accuracy of the guage at the bottom of the spectrum - where it matters most?

 

You saw an extreme variation, which is not usually the norm in my experience (10,200 miles so far on my 2004 HCH). I have found that I usually have about 1.5 gallons left in the tank when the "low fuel" light comes on. And that light sometimes comes on with three or two bars, never with 4 bars.

 

You are in good company. I've noticed that the fuel level is often underreported during idling, then increases when you step on the pedal.

 

No, no. When I left the house it was 4 bands, and 40 miles later 0 bands with the light on. When it went back to 3 bands (from 0!), the light was off. Sorry I wasn't more clear.

 

I haven't had enough tanks yet- but so far: low fuel light came on at 1 bar, drove about 20 miles and there was about 3/4 gallon left in my tank. haven't seen the bars flicker back and forth at all, but the other 2 times I refilled my tank at 1/4 tank/4 bars. I'm down to about there now, I'll keep an eye on it and post if I see anything weird going on- I was waiting for 1 bar anyway before I filled up.

 

You said you were on the bridge when it happened, where you on the incline or decline? I have had a few vehicle that did the same thing.
I have only been that low once on the HCH and it dropped about two bars while i was sitting on an incline to the bridge waiting to drive over and get gas.

Hopefully that is all yours was.
How much gas did the car take to fill up?

 

The float is usually at the front of the tank. If you're pointing downhill, the reading will go up, if you're pointing uphill, it will go down. I know for my 97 Civic the float must be at the front right side, because in a prolonged left hand turn (very long freeway transitions) the gauge will go up. On a prolonged right turn, the gas gauge goes down. The most accurate way to know is based on what it says your fuel economy is for that tank and how many miles since you filled up. Some quick math and that tells you how many gallons you've used.

 

Steve,
I've noticed this as well but don't have an explanation.
Once I drove to work of 46 miles & started off with 5 bands.
I parked with 3 left.
I started with 2 bars on.
Within a mile I was down to 1 bar and the fuel light on but still had about 45 miles to go and in a bad Atlanta neighborhood wanted to drive till the last one goes out, to a safer area.

(I hate how they place a giga-billion dollar business in these neighborhoods! Street dealers, ladies of trade, gunshots in the distance, right next to MARTA, Atlanta's "safe" public rail line)

I drove about 35 miles on that last bar before it went out, then filled with 11 point-something gallons of gas.

I remember once my wife & I started off near empty and after a mile or so 2-3 additional bars appeared.
She asked me why that happened and I simply replied:
"What do you expect, it's a hybrid car" (hee hee)

I've found the last 4-5 bars on the gauge to be less than reliable at times and in my case when the last bar goes out that's when I stop for fuel.

 

I think the computer seriously buffers the gas meter reading when the gas level is going up. It probably instantly calculates a low reading and displays it - so as to err on the side of saftey (i.e. you not running out of gas)...

BUT when it detects MORE fuel than the current reading, it waits a long time and gets multiple samples to ensure that this is correct (so it wouldn't behave like the example of AZCivc of going around a bend and showing a ton of fuel)

Here's how I came to that conclusion... I also experince the "almost instantaneous" drop in fuel bars every now and then (I live and work in a very hilly region). But today, when I filled the tank (12 gallons) and left the car on when it was filling (the engine was off ) it took me about 8 miles of driving before the gauge finally read "full".

The whole time it was going up bar-by-bar; VERY slowly.

 

I think it was a slight incline. I was getting my best tank mileage ever, so even though I shouldn't have worried, I did.