2004 Prius - Gauge Still Shows Full After 100 Miles?

The Gen 2 Prius (2004 to 2009) in North America used a bladder in the fuel tank to minimize evaporation. Unfortunately, the bladder behaves differently at different temperatures. In the Summer you may well get over 10 gallons in it and travel over 160 miles before the first pip disappears. In the Winter, the same car may only take 6 gallons and the first pip may be used in 40 miles. If you do your fill ups in the hottest part of the day, it holds the most. (most gas tanks, you want to fill up in the coldest part of the day, when gas is densest)

This also can bite you when deciding when to fill up, as the range after the last pip starts blinking is not a constant. (I have run out after 7 miles of blinking)

My best advice:
If you are riding with someone (mother in law) who will bring up running out of gas every time you meet, get gas with 3 pips
If you are riding with your significant other, who will bring it up to win fights, get gas with 2 pips.
If you are riding with friends you can trust to never tell that you ran out of gas, get gas with one pip.
If the last pip starts blinking, get gas NOW!

 

I have driven as far as 135 miles on a new tank of gas before the "pip" gets erased. So 100 miles is well in the typical range.

 

Without the tank bladder here in Australia, I get about 200 km

Hi thegoldenhand. Coming from a country where we don't have the tank bladder I can confirm that any time you truly fill the Gen2 tank, that the top pip on that gauge lasts at least as long as two or three "regular" pips. I would say that just about every time I fill up I get around 100 to 150 miles (160 to 240 km) on the top pip, occasionally even more.

About the only time that I wouldn't get 100+ miles on the top pip would be when I accidentally underfill the tank due to the petrol pump cutting out early.

 

Just remember that the gauge is a cheap indicator of approximate fuel level. For various 'social engineering' reasons, the top of the gauge is not at the real top of tank. Likewise, the bottom of the gauge is not at the real bottom of the tank. For cheapness reasons, each bar can represent a different amount of fuel. And the fuel sloshes around a lot, depending on driving conditions, leading to inconsistencies in when the display bars change. Sometimes one or even two bars may reappear.

And all that applies to ordinary cars. The bladder in your GenII throws another monkeywrench into any calculations you may attempt to make from the gauge. The gauge simply isn't accurate or linear or consistent enough to make solid calculations.

 

You are all right. On my '04, I notice that the next to the last pip lasts a very long time. When it gets to the last pip,
it seems to burn through that pip quickly then the "ADD Gas" on the MFD screen tells you to fuel up. Over all, I average 41 to 42
miles per gallon. Unless the tires are flat, I don't notice much difference in over inflated tires. An additional 2 to 4 psi is fine, but max side wall
pressure is foolish
The greatest difference I noticed in mileage was cleaning the mass air flow sensor. Before, I would fill my tank and do great for the first 100 miles or so. Then, it would just taper off and taper off. This made me feel bad to see that I was really trying to drive smooth and reasonable. Then I read that cleaning the MAF sensor made a change for the good.
Read or watch on the 'net for instruction on how to do it. I used throttle body cleaner and let it dry before I re-assembled the air cleaner assembly. I noticed a three to five mile per gallon increase in my mileage. My overall average has climbed to a little over 42 mpg. Imagine all the stuff that can bypass the air filter or gets through it. I will tell all that I find can be a change for the better.

 

So my 2007 does this too.... be careful though.

2 fillups ago, we went on a road trip. The tank was on FULL and I commented on, after 120 miles, the tank was still on full and no PIPs disappeared. A PIP ended up disappearing shortly thereafter, and the gauge seemed to "catch up".

Well, after 470 miles, I still had 2 PIPs. Super unusual for my Prius. I decided to fill up just because I was in the vicinity of my favorite gas station. It took 11.4 (IIRC) gallons

I am well aware of the gas bladder/"Guess" gauge issues but its never done this before. Heck, if anything, it will tell you that you are close to empty but only take 7 gallons. Ive never had it lie, and say it had 2 PIPs but was almost bone dry empty. So.... moral of the story, continue calling it a "guess gauge" and using the mentality that the gauge is not scientifically designed, and dont run out of gas like I came really close to doing.

 

I just had an event here, where the gauge was at full, then down one pip after about 100 mile, which is about normal. After I ignored it for a while it was suddenly at 4 pips. I had not driven enough miles to make that happen, but went to refill and could only get just over 3 gal. in the tank. Back to full on the gauge.

One is recommended to rely on the miles driven indicator rather than the number of pips.

 

This information looks very promising.

I recently bought a 2009 Prius touring model from Toyota. The first full gas tank I got from Toyota, I got 200 miles on it before the first pip dropped. I have not been able to replicate it with any new refuel tanks. I have tried ARCO gas, Chevron gas, even the found strategy driving (thanx to prius chat) and only hit 120 miles before the first pip drops. I have tried checking the tire pressure. I'm thinking about buying Kuhmo Sense KR26 with some 15" lighter weight rims to replace my current OEM 16" aluminum rims.

Thanx for the intel. I am adding onto the check item list:
1. Ensuring that the fuel tank is fully filled
2. Refilled at the hottest temp of the day. Shouldn't be a problem here in Fresno, we been hitting triple digits lately again.
3. Clean MAF Sensor

 

Very similar numbers to my recent long trip. 2 PIPs showing and I squeezed in 10.1+ gallons.
It was 88-95 degrees all through the driving hours, in case the heat exacerbated bladder (mal)functions.

 

This is good info to know! Thanks, JimboPalmer.

I tend to only have this "never decreasing pips" problem on long highway runs. The first time it happened I was very concerned. But once I made a stop (rest stop, restaurant, whatever) the fuel gauge behaved normally again once I started back up.

I had no idea what tehnology/physics were coming in to play to cause this, I just felt better whenever it went back to normal behaviour.
Now I can rest easy knowing it is to be expected anyway.

 

no

 

LOL !

I never experienced extreme variability in miles remaining once the last pip started blinking, but no doubt the rest of my life would have been more challenging had I ever run out of gas after telling my wife "don't worry, the car can easily go another 50 miles."

Common sense should also prevail here. The car does not know what the future road looks like. If the last pip starts blinking right when a long mountain climb begins, the AC is turned to full, and a 20 mph headwind starts to blow, there are not going to be many remaining miles till empty.

 

Indeed!

That would be applicable to any car. Ours is just so much more special

 

My advice would be to remember very well what the amount of your last fillup was ("G"). Next, have a good idea of what kind of mileage you are getting ("M"). Now, G times M (G*M) is how far you can probably go on your last tank. From there, I subtract 50.

So, I get about 50mpg. I guess conservatively and usually calculate for 45. My last fillup was about 9 gallons. I figure I'm good for 350-400 miles very safely. It also leaves me a buffer for situations where I don't have time for gas, but am going to get it as soon as I do have time. I get home and see I'm at 360, make a mental note to get gas soon. Then I get called to pick someone up and drive them somewhere, and I don't really have to worry, I can just get gas on the way home.

I usually end up filling up on the last pip. If I don't, that pip usually lasts a long while. Once returning from a roadtrip, I did over 70 miles on the blinking pip. The only time I ever ran out of gas, it was over 150... Both of those were in the heat of summer, though. I've filled less than 5 gallons from a blinking pip in winter.

 

Agreed. The instant MPG will always be more accurate and more telling of how many miles you can theoretically go than any hand calculation because if you are added 8.6 gallons on your last fill-up and you average 48mpg then you could theoretically go 412.8 +/- 20 miles.

One time my gas gauge was blinking, and I had to go 30miles so I added about a gallon, so I knew I could at least go 45 miles, but the last pip never stopped blinking. So, you basically can never exactly tell how many gallons are in your tank from the beginning, you can only know how much you put in.

 

I think it is documented somewhere that the Gen 2 needs 3 gallons to 'know' that any gas has been added.

 

Every time I read one of these "squeeze the last drop out of the tank" threads, I wonder if these folks are unknowingly doing damage to their fuel pumps. Somewhere in the forum there is a nice series of pictures documenting the disassembly of the bladder fuel tank. The pump is inside the bladder, but I'm not entirely sure of the placement and orientation. Still, with other cars that have in-tank fuel pumps you are advised to keep at least a half tank at all times to insure the pump is immersed and cooled by the fuel. I know if your pump fails it requires the replacement of the entire fuel tank for $$$. Somebody tell me I can quit worrying.