100+ miles and No change on Fuel Indicator

<div class='quotetop'>QUOTE(Green Speed @ Aug 4 2006, 07:04 PM) [snapback]297944[/snapback]</div>

I have the same problem. You are not alone.

 

i have had similiar weirdness although not that extreme. seems to happen mostly on longer trips @freeway speed.

have gotten home with 5 bars only to get up the next morning and have 6. to be honest with ya though, since getting CANVIEW, i really dont track bars anymore. did notice that on my current tank (378 miles @63+ mpg) that first bar disappeared at 150 miles, the 2nd at 165 miles...go figure

 

And you wonder why we call it the GUESS Guage?

 

Yep, it's nonlinear, and it doesn't behave the same way each time. But it *does* know when the tank is nearly empty, so always buy gas ASAP when the last pip starts flashing. Prudent drivers do so before that point.

 

I had the same problem driving ona 150 mile trip on the return I had 6 bars left when I started and drove about 90 miles and it dropped to 5, before too long the last bar was blinking and I actually ran it dry.....I was able to creep along the highway at about 50MPH for over two miles strictly on Batteries..NOw I make it a habit to fill up when there are three bars left.

 

<div class='quotetop'>QUOTE(Green Speed @ Aug 4 2006, 06:04 PM) [snapback]297944[/snapback]</div>

Was the temperature cool when you filled it up (like in the morning in the desert)?
You probably put dense fuel in the gas tank, which then expanded in the heat during the day. I noticed this the last couple weeks, I filled up on a cool day, then we got the heat wave and I stayed on full for over a week (140 miles, where normally it's about 80 miles before the first bar goes way). Then when the weather cooled a bit I started going thru bars every 30 miles, as I presume the gas cools (maybe the bladder too, not sure how that fits into the picture, but just the gas expanding/cooling makes sense in my mind, so why confuse things? :lol

My computed mileage was below normal too because I was probably able to put in more gas than normal. So this fill-up should be nice, I'm thinking.

 

<div class='quotetop'>QUOTE(nerfer @ Aug 7 2006, 04:58 PM) [snapback]299270[/snapback]</div>

Interesting explanation, Nerfer, & probably why PriusChat has been getting so many posts lately about the gas gauge being inaccurate.

It's rare (let's hope, at least!) to have a heat wave like we've had (in the whole nation) but perhaps, when we do, he had better all be extra careful about NOT trusting the gas gauge.

 

<div class='quotetop'>QUOTE(richard schumacher @ Aug 5 2006, 01:20 PM) [snapback]298326[/snapback]</div>

Even when it starts flashing isn't a very great indicator.

I know I've driven at least 30 miles after it's started flashing in the past, but about a month ago, it started flashing just after leaving the last gas station. The next one was about 15 miles ahead, so I proceeded. It ran out of gas after about 10 miles. I drove on the batteries about two miles 'til it gave up completely (on an uphill).
The temperature was close to 100 F, but luckily I got a ride. The gas station was about 3 miles away. I got a gallon of gas, got a ride back to the car, added the gas and drove to the station for a complete fill up. The total to complete the fill was 10.099 gallons. That's counting the 1 gallon already added.

Now it shouldn't have run out with about 1.5 gallons still in the car, but maybe it was because it was low and I'd been on a lot of hills. I'm guessing it shut down completely to prevent the the fuel injectors from running dry, but I don't know.

Anyway the gauge is definitely non-linear. A lot of times I do go 100 - 150 miles before the 1st bar disappears. It usually seems about right when it gets to the half tank level, but is again non-linear toward the bottom of the tank.

Dave

 

<div class='quotetop'>QUOTE(nerfer @ Aug 7 2006, 02:58 PM) [snapback]299270[/snapback]</div>

sounds plausible... aint it nice to get so much return from the little expansion that the gas goes thru that its noticable??

love my Prius!!

 

We frequently get to 150 miles before the first bar drop registers. Then it's something like 50-100 miles to the 2nd bar drop. As the tank gets lower, the bar drops occur more frequently.

It is odd, but it all evens out in the end. We have maxed at 525 miles on a full tank of gas, a few months ago. We tend to top it off anywhere below half empty.

 

I have been keeping track of the non-linearity of the gas gauge over my last few tanks, writing down on a notepad when the pips disappear. (I count down, so when I say the tenth pip, I mean going from full to 9 pips left.) After six tanks of gas, the tenth (or first depending on how you count) seems to disappear after a little over 140 miles. The next several pips (9-6) each last between 20 and 30 miles on average. Pip number 5 seems to last longer (sometimes twice as long) and then the remaining pips (down to 2, I always fill up by then) also last a bit longer than the earlier ones. In table form:

Pip number - Miles for pip - (Stdev) - Number of points averaged

10 - 143.5 mi - (35.25) - 6
9 - 23.2 mi - (6.22) - 6
8 - 32.8 mi - (8.44) - 6
7 - 28.8 mi - (4.32) - 6
6 - 35 mi - (9.11) - 6
5 - 39.25 mi - (16.2) - 5
4 - 42.24 mi - (13.26) - 5
3 - 64 mi - (---) - 1

There is quite a bit of variation, and this only covers a little over a month of driving (mostly in Michigan, with a mix of in town and highway) but as a general rule of thumb, I assume that after the first pip goes, all the other pips are about 30 mile (except for pip 5 which is higher) when I am trying to figure out when I will need to gas up. The standard deviation is pretty high on some of them (there is quite a bit of scatter) but I intend to keep track of this.

Yeah, I know, this all seems a little carried away, but I wish the gas (guess) gauge were a little more linear. I suspect that the first pip taking so long is actually done on purpose, to make you feel good. It makes it seem like the car is going to go forever if you fill up and the gauge doesn't budge for over a hundred miles. Same thing with the long pause at half. Can't prove it though.

As for the subject of temperature and its effect, have a look at this table:
http://www.aridtech.com/articles/art5_6.html
If you filled up your car at 30F with 10 gallons, and then moved the car to a place where it was 110F, you now have 10.6 gallons. However, this represents a huge chang in temperature (80 F) and a more likely scenario would be more like a change from 60 F to 80F in which case you go from 10 gallons to 10.1 gallons. Since the prius has an 11.9 gallon tank (or so they say) each pip should be 1.19 gallons if it were actually linear. A change of 0.1 gallons is still on 8% of a pip. Of course all of this is somewhat moot since the "tank" is really a bladder that changes with temperature in a way that is completely unknown to me. If Toyota were smart, they would make it mimic the way gasolines density changes so as to not have an overpressure if a full cold tank is moved to a place where it is warm.

Sorry for rambling for so long, but I have been thinking about this for a while now and you caught me in a talkative mood.

By the way, I am new here (06, package 3, seaside pearl.)

--Aaron

 

How many of you have watched this in your previous vehicle?

I did and my old '96 Civic did the same thing. Needle didn't move until past ~125miles, depending.

As I understand it, pretty typical of most vehicles out there, especially if you fill it to the top and a bit more.