False Fuel gauge readout?

The fuel gauge is notoriously innaccurate. You can do a search for "guess gauge" and see the many threads regarding its inaccuracy.

That being said, I'm not sure I would drive around with only one bar showing. Most of the time, I fill up when I get to 2 bars. Is there any reason you are only putting in 5 gallons at each fill-up?

 

<div class='quotetop'>QUOTE(chinito77 @ Jun 14 2007, 06:10 AM) [snapback]461453[/snapback]</div>

Do I detect the heart of a hypermiler beating in your chest? Another 30 pounds of gas (a full tank) may recalibrate the sensor. Where is your tp? Blocking the upper grill will also boost mpg.

 

For what it's worth my 2007's gas gauge is completely inaccurate and inscrutible.......

100 + miles without movement then sudden movement to a new position....

I keep a toshiba 110ct libretto subnotebook laptop in the car for record keeping and
i'm hoping to find some type of pattern on the gauge.

all the best
froley

 

Just a thought off the top of my head: Try filling the tank once, until the nozzle clicks off, just to see what happens.

 

Partial fills will throw off fuel computers on many cars. When you do a partial fill, the system has to work on just the float level, which is never completely accurate, and really bad on the Prius. Follow the previous poster's suggestion and fill it up.

Tom

 

<div class='quotetop'>QUOTE(Froley @ Jun 15 2007, 09:20 PM) [snapback]462843[/snapback]</div>

Makes two of us. I log all my mileage on my ThinkPad T42p, all the way back to when I first
got the car.

After 90-130-ish miles, the gas gauge goes down one notch. The only time it's even remotely accurate
is when it's half empty.

And are there long term bad effects to driving on empty? Thanks to the gauge being inaccurate,
I made it on empty until I had one bar for my battery because I ran out of fuel. Apparently, the Hybrid Synergy kicks in and you can only drive very slow, although it stalled twice (both times, about 150 feet from the gas station).

Paul

 

1. Running out of gas in a Prius does not do the battery any good. Don't make a habit of it.

2. Running out of gas in any modern car can damage the fuel pump because the pump is cooled by the flow of fuel. Replacing the fuel pump in a Prius requires replacing the fuel tank because the pump is inside the tank. You really don't want to pay for that.

 

<div class='quotetop'>QUOTE(chinito77 @ Jun 15 2007, 10:22 AM) [snapback]462308[/snapback]</div>

The definite thread must be "My first day with a blocked grill". Best ROI. I'm curious. When are you driving on I-95 and the Beltway so you can do a constant 70mph? It seems the Beltway is either Indy qualifying trials or a parking lot.

 

<div class='quotetop'>QUOTE(richard schumacher @ Jun 16 2007, 02:54 PM) [snapback]463126[/snapback]</div>

But this happening once isn't severely detrimental, right? The less stuff I have to replace
over the life of my Prius, the better.
Although I can't wait to see the supposed new version that gets around 80EPA (which is what, about 60 actual?).

PK

 

<div class='quotetop'>QUOTE(pkhoury @ Jun 16 2007, 06:20 PM) [snapback]463151[/snapback]</div>

Probably not. But that's a dangerous game of chance that nobody wants to lose.

As far as the original topic here, I'd like to pass along an idea I once heard. If you are committed to the partial fill-up, perhaps you should completely fill it once and then plan your refueling stops so that each one fills the tank again. In other words, calculate how far those five gallons will get you and refuel once you've traveled that distance.

Bonus benefit: You'll have a nice "reserve" of fuel on hand in case you can't get to the station right away.

In addition to concerns about the fuel pump are concerns about drawing impurities into the fuel system. I don't know how the bladder affects that, but in hard-shell tanks the impurities usually collect at the bottom.

- Justifyd

 

<div class='quotetop'>QUOTE(qbee42 @ Jun 16 2007, 01:34 PM) [snapback]463094[/snapback]</div>

I think you meant to say really bad on every Toyota. I've never driven any other brand that has such a hopelessly optimistic fuel gauge in the first quarter, then between 3/4 and 1/4 of a tank if you're really bored you can sit and watch it move downward, and then hang in the last quarter for an eternity! I figured the in tank bladder would improve the guess gauge on the Prius, but nope, it is the same as every other Toyota.

 

<div class='quotetop'>QUOTE(pkhoury @ Jun 16 2007, 06:20 PM) [snapback]463151[/snapback]</div>

Many people hit or beat the EPA number before the test was revised causing lower scores. Many more people will hit or exceed the "new" EPA number. If Toyota says the next gen gets 80mpg I believe it. Check out www.greenhybrid.com to see real world mpg.

 

<div class='quotetop'>QUOTE(pkhoury @ Jun 16 2007, 04:39 PM) [snapback]463095[/snapback]</div>

I just got my 2007 Prius, and I have logged all but 2 miles (that was on the car when I took delivery Friday). I realize that it is only 700 miles, but I noticed that the first (last?) bar took about 100 miles to turn off, the the others hurried on down so fast that I thought I would risk running out and have to fill before my normal second stop on my Twin Falls Idaho to Spokane Washington route. I had so much faith in all I read about the Prius, that I bypassed my usual first stop. It got down to 2 notches and stayed, so I fueled as usual in Pendelton Oregon. Computer said 51, calculator said 46, and either way I'm happy. I just want to learn how to interpret the gauge. Or just use one of the trip odometers.

Having seen other vehicles towed out of the southern Idaho roads during the hot days of the summer (usually failed fuel pumps according a friend that worked as a servicewriter in several dealerships), I don't want to take the chance.

 

<div class='quotetop'>QUOTE(Froley @ Jun 15 2007, 11:20 PM) [snapback]462843[/snapback]</div>

Inaccurate, Yes, but predictable. If I top off the tank, I get 125+ miles before the first indicator goes off. It depends on how much I overfill how long it takes for the first indicator to respond, it could go 150 miles. It doesn't matter how much gas you put in, the indicator won't respond until the overfill of fuel is used up. THEN it is very non-linear but accurately predictable. The next indicator will go out a about 36 miles, the seventh one at another 26 miles, the sixth/half tank indication will happen in another 45 miles, and the last half I haven't charted yet.

I don't know if this is the case for others, but I can count on these figures on my Prius. I'm concerned that by the time I chart the last 1/2 tank, I'll run out of gas. I end up filling the tank again before the weekend when they hike the prices!! I hope this helps.

 

<div class='quotetop'>QUOTE(chinito77 @ Jun 14 2007, 03:10 AM) [snapback]461453[/snapback]</div>

I had a similar experience. Before leaving on a 400 mile trip, the gas gauge was at 1/2, so I filled the tank, putting in between 3 & 4 gallons. The miles and mpg reset to zero as expected, but the gas gauge stayed at 1/2. I drove 200 miles and the gauge stayed at 1/2 the whole way. I then filled up again, and this time, everything reset properly. It hasn't happened again.

 

<div class='quotetop'>QUOTE(Froley @ Jun 16 2007, 12:20 AM) [snapback]462843[/snapback]</div>

So many people get bent out of shape about how the guage stays at Full for a 100 miles or so before it starts dropping.

I guess they never paid close attention to the analog needle gas guage on their previous car. If they had, they would have noticed that on a full tank, the needle most likely swung past the "F" on the guage and stopped on a peg on the top of the guage. The needle would most likely remain on this peg for many miles before it would move off it and then would take more miles before it dropped below the "F" line on the guage.

The digital guage in the Prius is no different. In the Prius, the "needle" gets digitally "pegged" at 10 bars. On an analog guage, the needle gets physically pegged on a real peg. The effect is the same.

 

<div class='quotetop'>QUOTE(Marlin @ Jun 19 2007, 12:47 PM) [snapback]464740[/snapback]</div>

With the added factor that on other vehicles with their analog gauges, the rate of fuel use causes the needle to drop rather faster than the rate of fuel use causes the 'needle' to drop on the Prius, so making the lingering around full rather more apparent.