Vehicle Gas Consumption - Accurate?

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Old 26 Apr 2012, 05:13 am   #1 (permalink)
DanielleOM
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Default Vehicle Gas Consumption - Accurate?


I was wondering if anyone has verified that the gas consumption
information provided by the Prius displays are valid. Have no reason to
doubt they are, however I find I do have to ask.

Thanks

Danielle
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Old 26 Apr 2012, 06:20 am   #2 (permalink)
Elmo P. Shagnasty
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Default Re: Vehicle Gas Consumption - Accurate?

In article <jnb744$1g1$1@dont-email.me>,
DanielleOM <danielle.e@reply.to.group.com> wrote:

> I was wondering if anyone has verified that the gas consumption
> information provided by the Prius displays are valid. Have no reason to
> doubt they are, however I find I do have to ask.
>
> Thanks
>
> Danielle


They are not. They are indicators, not gauges.

Do the math for yourself to see where yours lies.
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Old 26 Apr 2012, 06:47 pm   #3 (permalink)
Bruce Richmond
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Default Re: Vehicle Gas Consumption - Accurate?

On Apr 26, 6:13*am, DanielleOM <daniell...@reply.to.group.com> wrote:
> I was wondering if anyone has verified that the gas consumption
> information provided by the Prius displays are valid. *Have no reason to
> doubt they are, however I find I do have to ask.
>
> Thanks
>
> Danielle


They are reasonably accurate. Mine usually reads + or - 2 mpg for a
full tank. Try to be consistant about how full you fill the tank. If
you squeeze in enough to get to even dollars when you fill it will
cause one tank full to read high and the next to read low. Over all
it averages out.
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Old 27 Apr 2012, 09:15 am   #4 (permalink)
Pat
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Default Re: Vehicle Gas Consumption - Accurate?

On Thu, 26 Apr 2012 16:47:27 -0700 (PDT), Bruce Richmond
<bsr3997@my-deja.com> wrote:

>On Apr 26, 6:13*am, DanielleOM <daniell...@reply.to.group.com> wrote:
>> I was wondering if anyone has verified that the gas consumption
>> information provided by the Prius displays are valid. *Have no reason to
>> doubt they are, however I find I do have to ask.
>>
>> Thanks
>>
>> Danielle

>
>They are reasonably accurate. Mine usually reads + or - 2 mpg for a
>full tank. Try to be consistant about how full you fill the tank. If
>you squeeze in enough to get to even dollars when you fill it will
>cause one tank full to read high and the next to read low. Over all
>it averages out.


And, if your Prius has a bladder tank like my old 2004, you will find
that the pressure of the fuel dispenser makes a big difference in how
much gas you can get in. My county requires vapor recovery nozzles
while neighboring counties do not. I used to get from one half to one
gallon more in a fillup when filling up in a neighboring county. That
makes it hard to do consistent measurements. My newer 2010 does not
have the bladder tank. The bladder tank was an interesting idea, but
I am glad they did away with it. One time on a trip with the 2004,
the bladder must have folded in such a way, that I could only get 5
gallons into a nearly empty tank. The next fillup was normal and it
never happened again.

Pat
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Old 27 Apr 2012, 06:38 pm   #5 (permalink)
Elmo P. Shagnasty
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Default Re: Vehicle Gas Consumption - Accurate?

In article <u3alp7dtgc6lkcuc34r81ff5aelil9a19i@4ax.com>,
Pat <pat@nospam.us> wrote:

> And, if your Prius has a bladder tank like my old 2004, you will find
> that the pressure of the fuel dispenser makes a big difference in how
> much gas you can get in. My county requires vapor recovery nozzles
> while neighboring counties do not. I used to get from one half to one
> gallon more in a fillup when filling up in a neighboring county. That
> makes it hard to do consistent measurements.


You should never, EVER do the measuring across different pumps.

Go to the same pump across fillups, preferably at the same time of day,
if you want to have a reasonable presumption of any kind of accuracy.
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Old 27 Apr 2012, 08:08 pm   #6 (permalink)
bwilson4web
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Default Re: Vehicle Gas Consumption - Accurate?

On Apr 26, 5:13*am, DanielleOM <daniell...@reply.to.group.com> wrote:
> I was wondering if anyone has verified that the gas consumption
> information provided by the Prius displays are valid. *Have no reason to
> doubt they are, however I find I do have to ask.


Relative to itself, it is linear. So if you use them like I do for
mph vs MPG testing, go for it. But the Gold Standard is:

1) Use GPS or highway mile markers to measure and calculate the tire/
odometer offset. This changes over time so it needs to be calibrated
every 5-10,000 miles.

2) Consistent use of the same pump fed by an underground tank in a
state that had a functioning weights and measurement department.

3) Consistent fill-up protocol that should extend beyond the 'first
click'.

But now we're getting into the anal retentive region of engineering
metrics. <grins> ... where I live.

As a general rule, we've found the ZVW30 (aka., 2010 Prius) to be
about 6% optimistic but it is consistent. I have no idea what the
other models report and even though we have an NHW11, I really don't
care.

Bob Wilson
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Old 29 Apr 2012, 03:11 pm   #7 (permalink)
rjdriver
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Default Re: Vehicle Gas Consumption - Accurate?


"DanielleOM" <danielle.e@reply.to.group.com> wrote in message
news:jnb744$1g1$1@dont-email.me...
>
> I was wondering if anyone has verified that the gas consumption
> information provided by the Prius displays are valid. Have no reason to
> doubt they are, however I find I do have to ask.
>
> Thanks
>
> Danielle


I have compared one tank so far with my C, and I did not top off either
fillup, but did use the same pump.

Dash reading: 52.0 MPG
Calculated: 50.9 MPG

Doing my second tank now, and will top off both. Let you know the results
next week.


Bob


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Old 04 May 2012, 02:04 pm   #8 (permalink)
Michael Dobony
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Default Re: Vehicle Gas Consumption - Accurate?

On Thu, 26 Apr 2012 06:13:23 -0400, DanielleOM wrote:

> I was wondering if anyone has verified that the gas consumption
> information provided by the Prius displays are valid. Have no reason to
> doubt they are, however I find I do have to ask.
>
> Thanks
>
> Danielle


Check for yourself. I purchased my 2007 last month based on the display
mileage (47 on a long test on both city and highway). I just checked it.
Display said 44.8, but it was really only 39.8 That is combined highway
and city. That matches the best highway mileage I ever got on my 98
Corolla, down to about 33 after 240,000 miles on it.
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Old 04 May 2012, 04:02 pm   #9 (permalink)
DanielleOM
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Default Re: Vehicle Gas Consumption - Accurate?

On 5/4/2012 3:04 PM, Michael Dobony wrote:
> On Thu, 26 Apr 2012 06:13:23 -0400, DanielleOM wrote:
>
>> I was wondering if anyone has verified that the gas consumption
>> information provided by the Prius displays are valid. Have no reason to
>> doubt they are, however I find I do have to ask.
>>
>> Thanks
>>
>> Danielle

> Check for yourself. I purchased my 2007 last month based on the display
> mileage (47 on a long test on both city and highway). I just checked it.
> Display said 44.8, but it was really only 39.8 That is combined highway
> and city. That matches the best highway mileage I ever got on my 98
> Corolla, down to about 33 after 240,000 miles on it.



I filled up on the 1st of the month as I wanted to start off the month
noting in MS money the gas was toward the prius C. The sent me off wit
a full tank from the dealer. My calculations showed that I got 50+ mi
per gallon. I will check again next month. Most of my mileage was on
Connecticut two lane roads where speeds are typically between 35 and 50
miles per hour. From what I have seen the city rated mileage seem to
apply for those speeds. I was very impressed by how the car did one
mileage over rolling hills between Granby, CT and Barkhamsted, CT. I
did some highway driving at 60 - 70 miles per hour but not a lot.

Danielle
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Old 05 May 2012, 09:47 am   #10 (permalink)
PriusGeek
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Default Re: Vehicle Gas Consumption - Accurate?

On Thursday, April 26, 2012 5:13:23 AM UTC-5, DanielleOM wrote:
> I was wondering if anyone has verified that the gas consumption
> information provided by the Prius displays are valid. Have no reason to
> doubt they are, however I find I do have to ask.
>
> Thanks
>
> Danielle


I'm on my 4th Prius, have had at least one of each generation. Anal-retentive personality that I am, I have recorded for each tank the fill-up amount,displayed MPG, outside temperature, cost and calculated the actual MPG. Generally speaking, the Prius displays were all significantly optimistic in the MPG department. Overall, on 25 fills so far on my 2011, actual MPG averages 6.2% less than the MPG on the display.



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