My Gas Gauge

[staze]

So, I have a 2007 Touring Edition. Got it on December 9th. I've gone through a few tanks (yeah, uhh, 1800 miles on it already =( ), and I finally figured out why the gas gauge seems odd.

A lot of what I have read said people see their first pip disappear after 100-150 miles. I first noticed my first one goes away around 40-50 miles. So, this last tank or two, I really started paying attention to them. They're "gallon" based... The first one goes away after you go about the distance your average fuel economy indicates you should get per gallon. So, in this weather, my average has been 45-48mpg (my average is lower because I had a couple bad tanks and I think one time the attendant didn't get the tank "full"). So, first pip disappears around that point. Second 2x that, etc. So that should mean it's linear, yes? No... it gets more odd.

I just filled up after 350 miles, with my average at 47 mpg (2 pips remaining). While the pump was going, I did a quick calculation and found it should take about 7.4 gallons. Pump clicked off at 7.22. Attendant (yes, Oregon) started it again, and it went to about 7.3. Finished, powered on, full tank. So, that means I had a good 3-4 gallons left in the tank. I should have had 3-4 pips left if the gauge is accurate... or the last pip is worth about 3 on it's own, and I could have gone another 100 miles or so easily.

I'm not against filling up often. I'm not someone that's going to get every last drop out of the bladder... but I'm curious why my gauge seems to act completely differently than everything else I've read. Anyone else see this?

Thanks! And happy new year!

[Tideland Prius]

Hey! Happy New Year!

The gauge in the Prius is unlike any you've seen (or at least, I've seen). It is highly non-linear because of the rubber bladder inside the fuel tank.

However, one thing that's certain is that if the Prius says "Add Fuel" then do it even if regular calculation says otherwise. The reason is that the computer may be fooled into thinking there's less fuel then there really is and thus the light comes on when it does. Therefore, it's very likely that the car will "run out of fuel" before the tank is physically empty.

In short, fuel up when it says so because we can't use "traditional" techniques on the Prius.

With regards to the pips, it's different in the winter. I got up to 100+ miles on the first pip during the peak of summer. Now, I'm barely getting 50 miles before the first one goes.

[staze]

<div class='quotetop'>QUOTE(Tideland Prius @ Jan 1 2007, 02:22 AM) [snapback]369206[/snapback]</div>

In short, fuel up when it says so because we can't use "traditional" techniques on the Prius.

With regards to the pips, it's different in the winter. I got up to 100+ miles on the first pip during the peak of summer. Now, I'm barely getting 50 miles before the first one goes.
[/b]

That makes sense, and yeah, I've never ran a car out of gas, and I'm not about to start with my Prius.

I've actually wondered, how does it keep track of gas? A traditional method is to use a float in the tank.... but since there is a bladder, and theoretically no space in the bladder for something to "float"... does the computer just guess?

Thanks for the info on what you're seeing in the winter. Good to know I'm not crazy... but it still seems like the pips are directly related to the average fuel consumption. I guess I'll see for sure in the summer.

Thanks!

[gge5]

Just got my new '07 Prius last week. I haven't had to fill up yet (only down 3-4 bars), but I'm curious why they don't use a digital scale to weigh the tank? Seems like if they know the weight of the bladder itself then the remaining weight is pure fuel... I'm sure it's possible to have it securely attached.

Alan

[eagle33199]

The gas gauge is perhaps the most gripped about part of the Prius on here...

staze -

Interesting that you're observing that the gauge appears to be highly linear, i've never seen someone post that before. instead, it's usually posts about the first pip disappearing after 200 miles, or the last pip disappearing after 5... We don't have much data on the 07's, is it possible Toyota fixed this?

As for your estimation, the tank holds 11.9 gallons max (assuming the bladder is fully expanded). If each pip disappears after 1 gallon consumed, then they would all be gone with almost 2 gallons left in the tank, which would account for the gas you had remaining in the tank.


As it stands, i don't think any owner has really figured out how the gauge works... sometimes it seems fairly consistent, if not linear (ie each tank acts the same way, same distances, etc). other times, you have no clue whats going to happen because two pips disappeared on you over night. Regardless of what you may think is happening, do your best to avoid "doing the math" to see when you should fill up. if you run out, you'll be stranded, and risk damaging your HV battery should you try to limp to the station. The moral of the story is trust the car - when it says fill up, stop and fill up

[Devil's Advocate]

These observations are based upon over 250 refuels and some 86,000 miles driven:
With one pip remaining you have approximately 1 gallon of fuel remaining;
When the pip starts blinkning you can safely travel 25 miles (i call this yellow alert and have never run out of fuel within this mileage frame)
miles 25 to 30 are orange alert (possible that you will run out of fuel), and
miles 30 to 35 are red alert (likely that you will run out of fuel during this interval)
more than 35

[DaveinOlyWA]

a digital scale i think is a bit too much and the issue of an inaccurate gas gauge all stems from too many people bragging about 600 mile tanks thinking that if they can do it, everyone should be able to do it.

well that is not the case. just as some drive a car 200,000 miles without a problem while other vehicles start to distingrate at 65,000 miles, life simply aint equal.

ignoring your vehicles warnings to refuel is... well, lets not get into that. arguing about how far you can go is simply ridiculous.

its like saying my son should be 6 feet tall because his best friend is and they go to the same school and play on the same team.

make sense of that last statement, then maybe we can continue to argue about the gas gauge as if Toyota owed us something

[mikepaul]

Well, if you FILL the tank you can get over 120 miles before a pip goes out, but most people stop too soon.

When I'm too lazy to fill up, I get maybe 60 miles because there's usually at LEAST a gallon that can fit in there with some effort.

Sticklers to No Topping Off rules have probably been getting that 60...

[Frank Hudon]

best I've ever done on the first pip is 206 km about 128 miles, and I didn't spend 10 minutes trying to get it full. Rounded it up to the nearest dime and gone. Warm late summer day not really hot probably in the mid 70's. No A/C and level ground secondary hiway 90 Km per hour (55mph) in my Classic. Cold winter day in southern Alberta it was 86km about 53 miles. The bladder in the Prius is like a middle aged woman's bladder get it cold and it shrinks. YMMV

[Tideland Prius]

wow.. best I've done is 160ish km... worse was 50km when the car was brand new.