Back to the fuel gauge-my first blinking square

Indeed. Word is, Toyota is working on a software fix for this, hopefully it'll come sooner than later. Maybe they'll release it when the '05's come out, and they're testing it on them now? Hopefully. I wanna break a 500mi tank, let alone draw near that 600mile tank mark!

-m.

 

> I nervously proceeded until I came to a station where I refilled.

Just confirming with the Multi-Display should eliminate any need to be nervous. (Should I post that Distance/MPG chart again?)

What is your "fix" suggestion?

I've heard many ask for one, but almost none actually provide any requirements. And as a programmer, without requirements there is no way to know how you want the software changed.

Currently, the threshold is set to 9 gallons. And after the bladder has been broken in, you will hopefully see the blinking pattern on par with that.

My advice is change the way you perceive the blinking. In Prius, it is actually an INDICATOR to fill up soon (within the next 20 to 30 miles), not an almost empty WARNING like you find in most traditional vehicles since you do still have gas available beyond that 9 gallons.

 

Well, at 18K miles, I still see no pattern to the fuel guage on my 03. On the last tank of fuel, I was still one bar over 1/2 tank at 384 miles. A mere 100 miles later, I was at two bars on the guage. I stopped at 536.4 miles, and filled the tank, so that I wouldn't have to do so in the morning, and push getting in to work on time. I was still at two bars. That stupid bladder remains the ONLY thing that I dislike about my car. Granted, I don't have the descrepancies of the 04 cars, but I still don't like not being able to trust that guage. In my truck, I know the exact distance I can still go, when the low fuel light comes on. I've been able to do the same thing on every other car I've ever owned. The fuel guage, and tank on the Prius is stupidly overdesigned. Dump the bladder, use a rubber fitting on the opening of the fill neck to minimize VOC dissipation, and use a good old fashioned float and sender in the tank.

 

> still don't like not being able to trust that guage

That's why I ask for requirements. What are yours?

It sounds like you are asking for something else, the desire for a linear gauge instead. So it is accurate and trustworthy, you want it behave different.

Most owners are content with the 9 gallon non-emergency maximum capacity. And keep in mind that the decision was made to prevent people from actually running out of gas, since many ignored the warnings in the previous design and stressed the system by driving without gas. So if you'd like a change, request it in contrast to that current setup.

 

My Saturns all lit their low fuel lights when there was 1.5 gallons left in the tank. Since they had 12.5 and 15.5 gallon tanks respectively, I knew exactly what I would get out of a tank. My truck has a 35 gallon tank. The light comes on when I've used 29 gallons. None of the guages were linear, however, I knew exactly when the light would come on, and exactly how far I could go when it did.

The bladder in the Prius messes this up. The capacity changes with the temperature, and makes filling the car more of a chore than it needs to be. I expect to have to "mess" with fueling a bit with my diesel, as the fuel foams, and I've accepted this as a tradeoff for the longevity of the truck that it was installed in. Gasoline does not foam, and shouldn't be a process of trickling the last 1 or 2 gallons to get the tank full. Additionally, the funky way that fuel is "measured" with this thing, makes the guage behave differently, seemingly with every tank of fuel. I've had tanks run within .1mpg of each other, only to have wild fluctations in how the guage behaves. I don't care if it's linear. I simply want it to be predictable, and know for sure that when I've burned 10 gallons of gas, that I'll get 10 gallons of gas back into the tank.

 

When the gauge gets down to three bars its time to start thinking about filling up - no big rush but .... keeps me sane and calm.

 

I couldn't agree with you more, but I don't think that's something they can 'mod' in a software patch, unfortunately. Guess we'll just have to keep complaining and wait and see what happens!

-m.

 

Here's the problem as I see it: Toyota wanted to make sure we would not run out of gas, so they set the gas gauge to blink when there's really about seventeen gallons of gas remaining in the tank. (Okay. I exaggerate a bit for effect.) The result is that people know that the blinking does not really mean they are getting low, so they keep driving, and in the end are more likely to run out of gas because they can only guess how much gas they have remaining. Judging by postings here, there is a range from 2.5 gallons to one gallon in the amount remaining.

Here's what I'd like: a digital display telling me how many gallons (or miles, based on the current tank) I actually have remaining.

I don't know how the gas is measured in the Prius, so I don't know if this can be accomplished by a software fix. But it's what I'd like in a car that is otherwise as intelligent as this one is.

 

I couldn't resist jumping in. I, too, have been slightly puzzled but not really annoyed at the inconsistent fuel guage/bladder thingies. But, as has been pointed out, the purpose of the "reserve" fuel that doesn't show up on the guage is to keep you from running out the gas and starving the electric motor of the generator it needs.
Since we aren't doing overwater flights in these things, I don't see what the big deal is. We have computer readouts for mileage, so we know about how much per gallon we are getting, AND we do have a gas guage, finicky as it it. Why not just fill up when you get to the last bar and not worry about whether you got the same mileage this time as you did last time? I filled HUMU this morning just as the second to last bar went off, and put in just under 8 gallons. I think the bladder thing is stretching. Didn't bother me that there is a potential for 4 more gallons in there. It will come.
So, kids, be thankful that the bladders are getting bigger (unlike ours) and not smaller, so that each fill up will stretch it a bit more until we get something more like 10 gallons on a fill up.
Have fun, drive carefully
Bob

 

I have noticed that on my 2008 gen2 when I hit the last bar / single bar and immediately fill the tank it accepts just 8 gallons to brim.....indicating to me that thereʻs just under 4 left in the tank at this last bar increment based on capacity.... Iʻve talked to Toyota & of course after pleading ignorance got a confirmation from a toy tech that there is a service bulletin out on the issue. they wonʻt share the info though & want an hr. shop rate to check out. Anyone have hard info on this issue?

 

You should not assume that the fuel tank capacity is 12 gallons. Remember that the tank contains a flexible liner within which collapses and expands based upon ambient temp.

The tank capacity also depends upon how aggressively you fill the tank after the pump first shuts off.

There is a service bulletin regarding how to initialize the fuel gauge reading, but is that worth paying $150 or so to have that done?

I think you would be better off assuming that the fuel tank capacity is no more than 9 or 10 gallons unless your idea of fun is being stuck on the side of the highway, out of gas.

 

Please clarify Patrick...the stated capacity of the tank is 11.9 gals. Are you saying that because of the bladder the capacity is less. On our 2 experiments we refilled to the brim up with 7.9 & 7.6 respectively . will do one more iteration of one bar /immediate refill.

 

Correct, you should ignore the stated capacity.

If you really want to explore the actual capacity, carry along a supplemental fuel container and drive until the car runs out.

After adding fuel you will need to disconnect the 12V battery for a few minutes, then reconnect, so that the fuel gauge is forced to read the actual fuel level. Otherwise the system may ignore the added fuel if less than 3-4 gallons and you will not be able to restart the engine.

 

when i get below 1/2 full if I am driving around town I stop and fill it up. if I am on the road at about half tank I don't worry about the cars bladder I worry about my bladder. why why why push it I just can't understand what the obsession is. milage is mileage!

 

2008 Prius. Heard From Toyota National....they give an explanation of the function and no answer to the specific question ʻwhatʻs left in the tank +/- when you hit one barʻ to gauge range.. . State of the art engineering ambiguity.
Given the driving distances & times on the Big Island ....Iʻve advised my wife to assume fillerʻ up as you hit one bar..SOP.
Also "your vehicle is currently not involved in any related Special Service Campaigns or Customer Support Programs ʻ.
"The rated capacity in the Owner's Manual is correct, 11.9 gals. There are, however, some unique dynamics to consider regarding the Prius fuel tank.The volume of the tank can vary with temperature. To meet the Super-Ultra-Low Emissions Vehicle (SULEV) certification, the Prius fuel tank uses a sophisticated design that is basically an inner "rubber" bladder sealed within a steel case. The "rubberized" bladder expands less as temperature decreases. Therefore, using the traditional method for calculating fuel mileage (miles driven/amount of fuel added) is not reliable depending on when the tank is refueled. Also, the rubber inner tank is susceptible to fueling station nozzle pressures. More fuel can be added when fill nozzle rates are at the highest level and the tank hot, and vice versa.
Also bear in mind that with any vehicle, when reading “empty” on the fuel gauge, there is generally one to two gallons of fuel that is inaccessible. Automotive fuel tanks need a reserve of fuel that cannot be used, because water and sediment would otherwise be drawn into the fuel lines, causing damage and malfunctioning in the vehicle."

PS "Baldbubba"...you snide reply made no discernible insightful contribution to my fact-finding.

 

Ta, mate

 

I agree,,, so much! is like taking a bath every day,,,, you just do it,,, why worry about it! it takes the amount of gas it takes,,, sometimes more ,, sometimes less!

 

But it was cute! And maybe just a bit familiar (the bladder portion).

 

i find we have many engineers here, and some (most) have ZERO appreciation for humor! Being an engineer myself, I feel I am qualified to speak on the subject... I am not your average engineer,,, I enjoy beer wings and women.... needless to say when I go to an engineer convention.. I dont spend much time with fellow engineers... I just try to keep my cars bladder full,, an my bladder empty..... I enjoy the mileage my prius gives me,, however I in no way obsess over what the numbers are,, WHAT DIFFERENCE does it make! Kinda like women,, they are either ugly or pretty,, it is what it is!