// 2008 Prius Fuel Tank Capacity??? - Page 3

# Thread: 2008 Prius Fuel Tank Capacity???

1. ## I've been renting a 2008

I've been renting a 2008 Prius for two weeks while my other car is being repaired after a collision. My car is supposed to be ready in two days and I don't drive that much, so this morning I pumped in \$10 of gas (~ 2.6 gallons), but the fuel guage continues to blink like it's almost empty. I know I've got at least another 100 miles of driving before it runs out, but the blinking is worrisome.

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3. ## I just got a 2008 Prius and

I just got a 2008 Prius and filled it up for the first time when there was just one box showing, and it was blinking. I had a hard time getting gas to go in (the pump turned off automatically after I had put in \$1.24 of gas) and I eventually gave up at 7.5 gallons, which made the fuel gauge go up to Full.

Here's the interesting thing: according to the screen, on this tank of gas I had averaged about 45.5 MPG, but I got 420 miles and it took 7.5 gallons to fill the tank, which works out to 56 MPG! So either the mileage on the monitor was VERY conservative or my tank wasn't full after putting in 7.5 gallons, although the gas gauge showed it was completey full.

What do you think?

4. ## My mileage screen has been

My mileage screen has been EXTREMELY accurate. Normally accurate to +/- 2%. But I have to run several tanks of fuel to get a real calibration on the fuel consumption.

Mileage screen seems to be FAR more accurate than either the gas tank display, or the amount of fuel you put in the tank. Especially if there is a major temperature shift between fillups.

If you are not good at math, keep a small calculator with you and divide miles driven by MPG display to find out how much fuel you have REALLY consumed since last fill up.

Just remember that when you fill up in cold weather, your tank is NOT full no matter what the little bars on the dashboard show.

6. ## Why are you waiting until

Why are you waiting until the fuel gage is at one bar? The amount of mpg you receive will not change regardless of when you fill the tank. Also, you need to look at results over several fillings and weeks of driving in order to get an AVERAGE return on your gas dollar. As a rule of thumb, filling the tank at two to three bars will have you doing so when the tank is at about 20-25% capacity.

7. ## Hi again. I discovered what

Hi again. I discovered what was going on when my gas gauge was blinking -- almost empty -- and then I couldn't put more than 7.5 gallons in the tank. It appears that when the bladder is close to empty, it collapses, and then the gas doesn't go in easily, and it shuts off the pump. I suppose that's why Toyota recommends that you not let the tank get close to empty.

BTW, the reason to see how far you can go before the gauge is at one bar is not to determine the mpg, it's to find out about how many miles you can get on one tank of gas.

8. ## Interesting. I'm

Interesting. I'm considering buying my wife a 08 Prius. While I see much praise for the mileage, I see a lot of complaints about the fuel bladder tank.

Two thoughts come to mind.

1) Gschaut claimed 4 weeks ago that the fuel gauge was, at best, a "guess gauge". I assume the car "knows" how much fuel it has used so that it can calculate mileage based on the same fuel gauge, albeit a different interface to it. But if the gizmo that measures fuel usage is based upon how much fuel WAS in the tank and how much fuel IS NOW in the tank, AND that gizmo is not accurate, then the actual mileage will not be accurate either. To calculate mpg, you need to know: first how many miles, and second, exactly how much fuel was consumed. But if the fuel gauge is not accurate, then the mileage won't be accurate either.

2) If I put 10 gallons in today, and when its empty I can only put 7 gallons in because the fuel bladder is more rigid and won't expand correctly, then I cannot even check what kind of mileage I am actually getting with the car. In other words, there's no way to verify whether or not the car's calculated mileage is accurate.

Thinking of 1 & 2, its entirely possible that the Prius isn't really getting the advertised mileage at all. If the gauge is off by 25%, the mileage could be 25% lower (e.g., 36mpg instead of 48mpg). I might as well buy a Chevrolet Malibu with a fixed tank, 35 mpg, and OnStar !

9. ## I own a 2007 Prius. In

I own a 2007 Prius. In wisconsin. Gets really cold here in winter. First discovered the "bladder trouble" in January... Why doesn't Toyota tell people up front about the bladder design? Are they afraid it will scare some customers off? I also read at another website, that the U.S. market is the only one with this kind of fuel tank. Does anyone know if that is indeed true? My experience so far is that if I refuel at 2 "pips", at temps above 50 degrees, I can get 6.8 gallons or so into the tank before the nozzle shuts off. And tank registers "full". So far, this spring, I am refueling always at 2 pips, and have only travelled about 290 miles. But the MPG display claims I'm getting about 46 to 48 MPG. I have learned not to care anymore about how much gas is in the tank - I have learned to cope.

However, I feel Toyota should have been more honest about this bladder design and their manual sure as heck should be more clear about how and when to refuel, etc.

I consider this to be a design flaw. Anyone else feel the same?

10. ## There are TWO different and

There are TWO different and totally separate fuel measuring systems in the Prius.

The fuel "guess gauge" is similar to the normal fuel gauge in a car, in that it attempts to measure the fuel level in the tank. The only problem with Prius is that the tank is FLEXABLE and has a VARIABLE CAPACITY. One day the tank holds 12 Gallons, next week it only holds 8 gallons. So the tank level gauge is apocryphal at best.

The MPG mileage gauge is based on a fuel FLOW METER built into the fuel injector system. It measures how much fuel has FLOWED THRU the engine since the last time the MPG meter was reset. The fuel flow meter tends to be accurate within a couple percent. The MPG meter is like the gauge on a gas station pump, it tells exacly how much fuel has flowed thru it.

IF your MPG shows exactly 50.0 mpg at a total distance driven of 325 miles, then you have used up exactly 6.5 gallons since last fill up.

It does not measure how much fuel is left in the tank, but does give a very reliable measurement of FUEL CONSUMED.

IMPORTANT POINT: The Prius is NOT calculating MPG based on the fuel "tank" reading, but on a totally separate measurement of how much fuel has FLOWED from the tank to the engine.

11. ## Oops - to clarify my comment

Oops - to clarify my comment I just posted... I mean to say I refuel at 2 pips, and have logged about 290 miles between each refueling. The last time i remember ever going 400 miles before refueling is when the car was brand new before winter hit. the bladder hasn't been the same since. Am hoping if Wisconsin ever gets warm again and stays above 70 degrees I'll have better luck. I also want to say that it's important to keep bugging Toyota about this. This is a design flaw. It's not "normal". Name one other hybrid on the market that has a "guess gauge" for a fuel gauge! Or that spits fuel back at you (reported by other owners), or that decides one week to accept 7 gallons on a refill and then the next week, 3 gallons. doesn't make sense, and we paid good money for this car!

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