First fill up- can this be true??

<div class='quotetop'>QUOTE(ex minivan @ Jun 6 2007, 12:35 AM) [snapback]456322[/snapback]</div>

That is a realistic number, congrats!

It is still probably slightly underfilled if you were at a flashing pip, but I may be wrong. I think that since I've had my car (have put 1200 miles on it) that so far I have underfilled everytime. I'm too nervous about trying to "top-it-off" and then have overflow.

better safe than sorry!

 

Evan is correct...each gas pump is different in when it shuts off, and the bladder in the Prius gas tank is susceptible to the ambient temperature. Definitely trust the display to give you the most accurate idea of your mileage.

 

For what it's worth, I have always filled my 2007 purchased in Jan with the pump handle locked on the fastest setting. After it clicks off, I try to put a little more in at slow speed, and it always clicks off again, almost imediately. Usually put in about 8 gallons, and have never had it splash out with Fred Myer, Shell and Union 76 pumps.

 

I did my first fill up a few days ago - was down to 1/2 tank according to the guess gauge. I filled slowly, and the pump didn't shut off. I noticed when the fuel appeared at the nossle. Of course it "burped" (air only which splashed a little fuel) when I removed the nossle. A little fuel on the ground, but not too bad.

Now, because the dealer had "filled up" before I got the car, and didn't overfill as I did, the calculated mileage was 8 l/100 km. Not very good.
MFD however, said I did 4.7 l/100 km. Much better. Looking forward to the correction when I next fill up (and yes, I'll do it a bit differently to avoid over filling).

I put in 27 litres, and if it was truly 1/2 tank it should have been 22.5. Difference was probably caused by three factors:
1. Gas gauge is not that accurate - 1/2 tank indication probably isn't really.
2. Dealer didn't fill all the way.
3. Extra gas in the filler tube.

I don't recall ever looking forward to filling up a car with gas as I do with this car.

BTW, the fuel gauge didn't start to drop until I went 250 km after filling it so full. Now THAT's amazing!

 

Keep a journal to track every fillup, and the mileage.
Average it out over 4 or 5 tanks, to get your mileage.
Apparently, the internal bladder in the tank does do things to the amount of gas you are able to put in the car, so using an average is really the only way to get accurate numbers.
Besides, it's really fun to watch your mileage steadily improve, as you learn to drive the car more efficiently!

 

Would this mpg calc methodology work:

Go until fuel warning comes on.
Always fillup with same amt (gals) each time ie 8gal.
Miles/8 gal = mpg.

 

<div class='quotetop'>QUOTE(MickeyA @ Jun 6 2007, 12:21 PM) [snapback]456591[/snapback]</div>

No, it wouldn't work. The reason you need to "fill up" the tank is because that is approximately the amount of gas you used since your last fill up.

If you put in the same amount of gas each time regardless of whether it actually filled the tank, how do you know how much gas was actually consumed the next time you fuel?

 

I've tracked every gallon through 112 fillups since 2/06 to get a pretty solid average... A few things I know for sure..

1. My last pip is rarely blinking but I almost always fill up more than 9 gallons, often high 9's into the 10's and a few times over 11. You didn't get filled up with <9 on a tank with the pip blinking. Figure another gallon on your calculation and deflate that smile for having gotten 60mpg... you were closer to 50... which isn't bad, but it's not 60.

2. The MFD is way off. somewhere more than 5% to about 8 or 9% off and it's generous to itself... If it shows 57, I can hope the actual mpg was 53 or 54.

3. I fill it up on the slow notch, then pull the nozzle out so the tip is barely in the hole and pump about .7 to 1.2 gallons in without a burp so that I can hope to get 4 full days of commute between fillups, otherwise 3 days is max. If you try for all the way full, you'll get the burp.

4. On any single tank, you can at best 'think' you got a certain mpg or performance... After 20+ tanks, it gets harder to have a skewed average. If you fill +.8 gallons or -.8 gallons, you are getting hugely skewed results. take an example, you actually burned 10.0000 gallons over 500.000 miles.. actual is 50.000 mpg. When you fill a single tank and it clicks off at 9.2000 gallons, you can calculate it out and tell all your friends that you got 54.3mpg... Did you? Or, if you squeezed it to 10.8 gallons, you can then say you got 46.29 gallons. That sucks...

So, get your averages on actual gas purchased over odometer miles driven. The MFD is reliable for me, just reliably wrong. Until you know what that skew is, you can't report anything based on it. Get it on a grid..

http://www.daronspicher.com/php/prius/priusgasgrid.php

You track it like that over long enough time, it's hard to argue with the numbers.

 

For any single tank, the Car's estimate is better than taking Gas in/miles.

Once you get over 5 tanks or so, Total gas in/total miles is the best.

 

<div class='quotetop'>QUOTE(daronspicher @ Jun 6 2007, 12:40 PM) [snapback]456642[/snapback]</div>

I agree with everything except #1. Never have been able to buy that much gas. If the tank to tank averages are consistant then I say the numbers are "good". If tank "A"'s mpg is high and "B"'s is low then there was an error that corrected itself. Most likely the error was not filling the tank for whatever reason.

 

FWIW, I usually pump between 11.2-11.7 gallons per fill-up.

 

<div class='quotetop'>QUOTE(JimN @ Jun 6 2007, 11:18 PM) [snapback]457105[/snapback]</div>

That's because NJ doesn't trust us to pump our own gas, Jim! Over 62 fills, I've only had 1 fill that was over 9 gallons. And 3 others that came close. And I've only seen the blinking pip once or twice.

<div class='quotetop'>QUOTE(JimN @ Jun 6 2007, 11:18 PM) [snapback]457105[/snapback]</div>

I've seen this little phenomenon myself more than a few times. My last 2 fills were like this.

• 344.1 miles / 6.553 gallons ---> 52.51 mpg (MFD: 57.0)
• 438.7 miles / 7.096 gallons ---> 61.82 mpg (MFD: 57.2)

The average of both tanks ends up around 57.1 or 57.2.

 

No criticism here, just a little reality check. If the MFD is within 10% that is accurate! We're not talking about using graduated cylinders, temperature compensation for volume, etc. We're talking injection time vs distance. I've had "driving computers" in my cars for over 20 years now, and they are never "dead on". 10% is pretty good for something that is designed to just be an "indicator". Remember, engineering accuracy is 5%.

 

<div class='quotetop'>QUOTE(David Beale @ Jun 8 2007, 09:47 AM) [snapback]458001[/snapback]</div>

Too bad there isn't a setting in the mfd where I can input an 'offset'... If I put -2.0 in mine, I'd be a whole lot closer to actual...