Only 320 miles to a tank?

Not sure about Prius liftback, but the Prius C has a 9.5g tank and when it beeps at me, I can only get about 8.5g, so that's an entire gallon (assuming its only 1.0 gallon and not more) that's not technically being used.

Hope that helps.

 

I haven't tested it, but I'm guessing about 1.0 gallon's worth. (42-ish) from what you said. But you should be getting over 400 miles per tank. If you're getting 42mpg, and say 10.5g tank (before it beeps) = 441.

 

There are many posts regarding this question and the Gen 2 badder. Some people have had mixed results. I personally wouldn't risk running out just to "say" that I got a certain number of miles out of a tank. As long as the fuel economy (mpg) numbers are good, who cares how many miles you get to a tank?


iPad ? HD

 

OP, how many gallons are you putting in, once hit the flashing pip?

We've commented on how many usable gallons there seem to be on the Gen 2 many times. One such thread is at !!Fuel Bladder Frustrating Me!! | PriusChat. Compounding the uncertainty, besides the guess gauge, the bladder tank has variable capacity, depending on the temp.

Also The Gas Gauge Says Full, But That's Not Quite True: NPR | PriusChat, might be insightful, even though it's a Ford engineer talking.

The most I've ever put in at was 9.975 gallons. I think I was down to 1 pip and don't recall if it was flashing.

I recently put in 9.304 gallons (went 2 or 3 clicks past the auto-stop) at 1 pip (not flashing yet) after traveling 394.1 miles.

 

I have a 2008 Prius. According to the manual when the bar is blinking, there is less than 3 gallons in the tank. I don't know exactly how much less. I've never pushed it all the way to see. I can tell you I've filled up numerous times on 1 bar (not blinking) and there has always been a little over 3 gallons remaining in the tank. I hope this helps you.

 

Not much. You should fill up immediately upon blinking. In general you should fill up on one dot before it starts blinking. Because the Gen2 (2004-2009) has a bladder (flexible) gas tank there is a lot of uncertainty. If you push it, you will run out of gas one day. The problem with that it is, you do not want to run down your HV battery to zero charge because that is often good-bye battery.

We get a lot of 320 mile tanks in the winter when MPG is less and the bladder tank only takes 8 gallons. In hotter summer weather the bladder tank will take 9-10 gals and your MPG may get closer 50 MPG range. Our personal record is about 485 miles and we do this often in summer. Forget about the 11.7 gal figure, I think that is not counting internal hardware inside the tank. Your effective tank size is as low as 8-9 gal in cold weather around 10 gal in summer.

 

wjtracy is spot on with his explanation. I see the same thing on the 09 Prius I drive regularly. I am just now feeling comfortable with the guess gage. I have never ran it down to the flashing pip. I have run it down to the last pip. The most I have ever put in is a little over 8 gallons. With the warmer temps we have been having recently, the bladder has started to expand again. I travelled a little over 400 miles this tank and had two pips showing when I refilled. It took 7.23 gallons. The tank before I travelled almost 400 miles, had one pip showing and it took 8.12 gallons. 8.12 gallons is the most according to my records since I started driving the Prius in 2011 a month after Valentines Day. During the winter time, I usually refuel between 300 to 350 miles and during the summer time, I usually refuel between 375 and 400 miles. It took a long time before I got used to the Prius guess gage. Even longer to begin to trust it. I am one of those types who does not like to run out of gas. I did that once a LONG time ago. It was not fun thumbing on a high speed freeway to get a ride to buy some fuel and pay for a gas can too.

One thing I found that really helps me. When I fill the car, I always fill it at the slowest pump speed and I always allow the tank to vent a couple of minutes before I put the nozzle in the tank to refill. I seem to get more consistent fills when I vent and pump slowly.

Good luck to you!

Ron

 

During the summer months you will do much better. I keep meticulous records on mileage and fuel used for my Prius. I typically wait until the blinking light to fill up. Last summer: consecutive 544 miles, 10.66 gallons, 542 miles, 11.18 gallons, 544 miles, 10.89 gallons, 567 miles, 11.46 gallons, 593 miles, 11.74 gallons. (Summer of '12)

During the winter months my mileage drops substantially. Last winter: consecutive 385 miles, 9.32 gallons, 380 miles, 9.12 gallons, 343 miles, 9.15 gallons, 358 miles, 8.94 gallons, 346 miles, 8.82 gallons. (Winter of '12-'13)

Some of the disparity would include temperature, winter blend vs. summer blend of fuel. I have also never run out of fuel, however, am a member of triple AAA should anything happen! Hope this helps!

 

I once ran out of gas on my Gen 2 only 7 miles after the last pip started blinking, other times I have gone 30 miles while it is blinking.

I you wait until it starts blinking, someday you will need to carry 3 gallons of gas to it.

Ran out of fuel AND battery!! | Page 3 | PriusChat

 

I bought an 07 Prius couple months ago and I've been curious about the missing 2.5 to 3 gallons after usually putting in around 9 with a capacity of almost 12. I have been thinking about how much further I could go with a tank capacity of 11.9 gal. (I stop pumping at the first shut-off to try to get as consistent as I can figuring mileage. I know stations and pumps are not consistent, but I'm trying.)

So when last pip started blinking a few days ago at 438 miles with display showing 47 mpg on this tank, I figured I could go on for quite a bit, the question was how far. I have read on here somewhere that you can probably go your display mileage times 10 gallons no problem. I debated whether I should stop at 470 or take it on to 500 or more.

I know a lot of people on here say the low fuel warning is more than sufficient, but to me it's not a low fuel warning if it kicks on too early -- it's an almost-but-not-really-yet-getting-low-warning! 3 gallons left is not low fuel in my thinking.

So on my way to work yesterday, at 502 miles on the tank, with display reading 47.3 mpg, my car display lit up like the 4th of July. The Master Warning Light came on along with several others. Now I wish I would have taken more time to look at the display/messages, but I just assumed it was yelling at me about needing fuel. I ducked into the closest gas station with decent prices, just kidding, the closest station, and filled er up. (I only went about a 10th of a mile to get gas.)

Everything seems to be back to normal after getting gas. Calculating by fuel added, I got 47.9 mpg on the tank. But how much fuel did I add (to get the first pump shut-off) ... 10.497 gal.

I keep reading on here about topping off and why it is and why it isn't a good idea. So I don't know what to believe. I want to top off so I can better figure my mileage more accurately. I also want to top off so I can get closer to utilizing a 11.9 gal tank, not a 9 or 10 gal tank. Isn't it more efficient to stop for gas less, and isn't more efficiency part of the magic of the Prius?

My plan is either to keep filling up to first pump shut-off and then stopping for gas at display mileage x 10 (47.5 x 10 = 475 miles) or maybe I'll try pumping an extra gallon after first pump shut-off and then going x 11. I don't know yet.

Little bit more background ... My previous tank (before this one) took 10.5 gal to fill up when I thought it would only take a little over 9.5. I guess that pump was set to shut off later than the average pump so you get more gas there. My display was reading 49.1 but calculated by gallons and mileage to be only 44.4. Usually they are much closer to each other than that. -- So when a typical tank took 9.5 to fill up and then this previous one took 10.5, it was closer to tank capacity than I was used to. I'm guessing that instead of the typical 2.5 to 3 gallons hiding out somewhere I was closer to only 1.5 gallons in hiding, leaving me with less than I thought I had when the last pip started blinking.

Did that make sense? Instead of having the usual 2.5 to 3 gallons left when the last pip blinked, maybe this time I only had 1.5 left, which I used when I went from 438 to 502 miles. I don't know. Maybe it's best to stop at mileage times 10 since I don't know how full the tank is without topping off. ?? I wonder if I ran out of gas or maybe some system started to struggle as the last bit of gas sloshed around.

 

Prius attitude check needed here! You need to try to give up on squeezing the most miles out of tank. You really need to fill up when you get to one pip. If pip is flashing you are risking disaster. Disaster being running out of gas, and then running HV battery down. This could damage HV battery, and that means trouble in river city. About 9 gallons is typical for the summer fill-up of the flexible bladder "guess" tank. The only thing experienced Prii drivers might try to do is give the guess tank a chance to vent adequately when filling up. This means leaving the cap open a few minutes and pumping gas in slowly. We never top off and never run past one pip if we can help it.

I never heard the 10 x MPG rule either, but the problem with this is computer can easily be off 5 MPG and that leaves you in Timbuck2. Don't get me wrong it is the first Prius frustration they give you such a small tank, but there is nothing you can do about it. There are all kinds of emissions equipment in the guess tank, so replacing with a bigger tank is just not an option.

 

The only other thing I would add to this discussion is the importance of keeping the internal fuel pump immersed in fuel. I'm not really sure where the pump is located in the tank, but they are usually near the bottom. That means a half tank or better. It provides cooling and lubrication. If the fuel pump fails, you will be replacing the entire fuel tank for what I would imagine is BIG bucks.

 

It makes sense and you are confusing yourself because you do not realize that you do not have a tank. The methods you are trying to use like average FE per tank and gallons remaining in the tank once the fuel sender reports low, and those sorts of things all rely on you having a tank. A rigid form that accepts N gallons any time and every time. Using this consistency you can calculate all sorts of goodies and you can pretty much figure out what the mapping of fuel sender to pips is.

HOWEVER, you have a North American Generation II Prius. This car does not have a gas tank. Yes that's right NO TANK. It has a fuel bladder. It is a flexible membrane that expands and contracts, billows out, and folds over. The capacity of the tank depends on the physical shape of the bladder when you go to fill up, whether or not it is folded over, outside temperature, and other such variables.

You are going to get stranded a lot more if you want to play this stupid game with your car. When the last fuel pip starts blinking, you immediately need to fill up. There is no way of knowing if you have 3 gallons left, or you are running on fumes. You don't know what the shape of the tank was when you last filled up, and you don't know what the shape of the tank is as it is blinking.

 

I agree 100 percent with the above info. Your best bet is to simply fill the tank when the guess gage gets down close to the bottom. There have been several reports of folks running out of gas one time 50 miles past the blinking pip and then other times running out 7 miles past the blinking pip. The bladder is the problem, and the guess gage compounds it. If you want to play safe, fill up when you hit two pips. If you feel comfortable continue on to the last pip. Anything after that is really like Russian roulette. Sooner or later you will lose. Also, if you find yourself on the side of the road, you will learn real fast that the Prius will not restart until you have a minimum of three gallons of fuel once it runs out. Also the Prius has a limit of how many times the engine will try to start once it is out of fuel. If you don't get it running before the limit pops up, then you have to be towed to Toyota and pay the man to reset the system.

Moral of story, buy gas when you get to two pips and don't worry about it. Remember you are still getting excellent economy and the lowest of all emissions. They put the gage on the car for one reason, to tell you when to buy gas. End of story.

Ron

 

Thanks for the input. I especially appreciate the information about the bladder and fuel pump. And I hear you loud and clear that I cannot expect to go 60 miles after blinking last pip just because I did manage to this time. -- I think I'll relax a little about the missing 2-3 gallons and focus more on enjoying the 9 or 10.

Now that I have filled up several (6) times, here's what I find: Total miles for the 6 fill-ups divided by gallons used = 45.9 mpg. And calculated adding the 6 tank display mpg and dividing by 6 = 47.6 mpg. Looks like 3.7 percent higher on the display (I understand it's common for display to read optimistic). While the difference between calculated and display was as high as 11% on an individual tank, it averaged out to 3.7 percent difference with the 6 tanks.

Of course I don't know what is really the true gas mileage for these 6 fill-ups because of the differences in how full the pumps go till that first shut-off, slope, temp and what not (at least for 1st and 6th fill-ups), right? I'm wondering if the display will be more consistent, even though a little optimistic?? By calculating based on miles driven/gallons pumped I think I will get more variation, sometimes higher than true and sometimes a lower number based on when pump clicks off and such factors. Seems to me like my best guess on my true gas mileage will be display x .965, or something like that. Sound about right from what others are seeing? Do I need to bother with the calculation of mileage divided by gallons?

 

N.J. I have to inquire how you are pumping so much in during the summer. Venting before filling? Topping off? Getting gas at the blinking light does not give you into the 11 gallon range, right? I am curious about your strategy because you would not do it if you didn't have some good reason. -- Is your bladder larger than the average bladder?

 

Best calculation is as you are doing with total gallons over total miles. The more gallons you use the more accurate your average. Miles driven vs. gallons pumped is not just more variation, it will usually be completely inaccurate. For the GenII there are reports anywhere from +/- 5% error on the mpg calculation. So you are within that range. Mine reads 1% or so optimistic over the life of the vehicle.

Topping off is very very bad. If you overfill the bladder you can potentially do a lot of very expensive damage to the bladder area. When the pump stops, stop pumping. I usually just go to the next whole dollar amount of whole gallon.

The last blinking pip might be 3 gallons left, it might be 0 gallons left and just what's left in the tubes. You don't know and you can't tell.

To maximize bladder fillage, pump slowly. Also if you are in a state with emission traps on the pumps, then turn it upside down. First thing when you fill up is open the cap and let it breath, sometimes up to 5 minutes to let the bladder expand if it had folded. Then pump as slowly as you can tolerate. You can stop halfway and then again wait. This will maximize fuel in.

Personally, I jsut fill it like any other car and leave. In and out quickly, no tricks, no games, no waiting. I accept the bladder is variable and when the car says it needs fuel, don't question it. The car takes care of itself, stop trying to outsmart it.

 

Thanks for the filling tips!