142MPG? I need some help here.

Wait, what makes you think it's getting 142 MPG? How many miles total have you driven it, and how many gallons of gas total have you put in it?

The fuel gauge is very nonlinear and the tank volume itself is variable, so you can't judge anything from how fast or slowly the bars on the fuel gauge fall. Or are you saying that the bars never change? (But then how did you know when to buy gas?) In that case, time for a trip to the dealer for warranty repair.

 

Your gauge is normal. Because of the odd size and bladder system in the tank,
you may go 150 miles before the first pip disappears on the gauge. I've found that if the tank is completely full in the summer I can use three gallons or 150 miles before the gauge changes. Then it's about a gallon or less per pip for the rest of the tank.

 

It's too soon to say if anything is wrong with your car.

My question is, how did you manage to pump 12.2 gallons into a bladder-equipped Prius fuel tank? Most owners are lucky to get 10 gallons in, even with multiple click-offs.

I am wondering if your gas pump cheated you.

 

12. 2 gallons into a 11.9 gallon tank and you still delude yourself into thinking you did not top off?? you are either

1)getting ripped off by the gas station you used

2) using a gas pump that was malfunctioning,

3) putting WAAAAY too much into the gas gauge (more commonly referred to as "guess gauge" btw)

the only thing i would go by is that when the last bar starts blinking you should stop and get gas. everything else on that gauge is a very loosely formed guideline and should never be used to determine what your gas mileage is...

and btw, what does your display say your mileage is?

 

I have unintentionally (poorly adjusted pump) completely filled the tank twice and intentionally done so another few times. Each time I go about 200 km or 120 mi or maybe a bit more before the first pip goes out (highway). In the city perhaps a bit farther.

I -always- check after filling to see if I can see the fuel level in the cars' filler pipe. If I completely fill I can, but if I rely on the shutoff of the pump I never can, just the bubbles which settle out out of sight quickly.

Completely filling the tank is not really a good idea. The fuel can be forced into the vapour recovery system and get between the bladder and the tank body, where it will cause corrosion damage. New tank is $400+!

What happens (I think), is the fuel expands after you pump it in. It has nowhere to go so pressure builds up and forces it through the vapour recovery system. If it's cool out (less than 50F) or if you immediately head out on the highway and burn at least a gallon in the next 30 min you would be ok as that's about how much the fuel in the tank will expand (about 2.5 litres - 50F fuel and 80F ambient temp - last time I calculated it).

 

12.2 gallons? Yeah, something's fishy there. I can rarely squeeze more than 35L (~10gal) into my Prius, even when near-empty. However, if your tank was "very" topped up, it would explain why the first pip took so long to disappear.

On a totally different tangent, is there another driver on your car who may be playing a trick on you by topping off your tank after you've driven some 75 miles or so? It won't reset the Consumption screen 'distance' automatically with a small fill.

Remember, it *IS* April 1st, after all...

 

i dont think the OP is using the consumption screen. just going by the gas gauge thinking each pip is a tenth of the tank.

all in all, the display is very accurate at telling you what your MPG's are. many complain it reads to high, etc...but i think its by far, more accurate than pump readings, etc...

to really get a true picture, you need to track both the display readings (making sure you manually reset every time you fill up. use trip A or B also so you get mileage in 10th's) for several fillups. i would not even start to make conclusions until you have done a minimum of 3-4 fillups.

 

Nope, it's not nearly that linear. Whatever the MFD shows as your current MPGs is pretty nearly correct because it counts actuations of the #1 (?) fuel injector. It doesn't use the fuel gauge.

 

I think the record I've seen on PC was over 200 miles on the first pip. I'm certain that the insane hypermiler that went over 1,000 miles on one tank probably put the 200 mile pip to shame, too.

 

I wouldn't even start to worry about it until you get to over 250 miles. On the flip side I was down to just 1 PIP and only had a $20 bill on me, so I just put the $20 in the gas tank (6.5 gallons @ $3.069) and my gauge only went up to 4 PIPS and has stayed at the 4 pip level for 85 miles now.

 

I'm a new Prius ownere and need some input here from you kind folks. Maybe I'm a little slow (my family would say "yes!"), but let's say I'm going on a trip for a thousand miles, and I don't want to fill up the gas tank until I'm down to my last 50 miles or so. If the gas gauge is not that accurate (at least until the last pip starts blinking), then how will I know how much further I can go?

Should I just use common sense and assume the MFD mpg (let's say it's showing 48mpg) is fairly accurate and multiply the mpg by, say 10 gallons and therefore conclude that I can go at least (48mph x 10 gal = 480 miles) without having to worry about it?

On previous cars I liked to take the fuel gauge down to a pretty low level at times just to see how many miles I can get out of it, but on a trip I wouldn't want to get stuck out in the middle of nowhere by assuming I had more fuel than I really did.

Any thoughts/suggestions/ramblings are welcome.

Thanks!

 

It is not wise to assume you have 10 gallons of fuel in the tank. In the winter, since the bladder shrinks, you might only have 8-9 gallons.

Since the fuel tank capacity is variable and the guess gauge is not aways predictable, your desire to drive until you have 50 miles remaining (which means one gallon of gas) may result in out-of-gas situations.

Unless you don't mind running out of gas, its better to be conservative and refuel when you see two bars (or more) remaining on your fuel gauge.