"Elle" <honda.lioness@earthlink.net> wrote in message
news:uZkxf.8215$M%4.5531@newsread3.news.atl.earthl ink.net...
>I have been watching my 91 Civic's mileage particularly
> closely since about October. This includes, for the
> overenthused, watching the fuel tank gage. A few times I
> have thought to myself, "Darn, it's reading just about
> half-full, and I usually have at least X miles by this
> point. The trip odometer is at more like X-50 miles right
> now." So I would predict that the next fillup will yield
> stats indicating really bad mileage. But on the contrary,
> apart from a few weeks where I had the timing messed up, it
> looks good, for winter.
>
> As people have indicated here recently, gas pumped in the
> summer from a nice cool underground tank (typically) expands
> once in the car's tank and while warming to ambient. This
> makes sense. In this vein, could it be that, while driving
> in the summer, the fuel tank gage reads particularly
> disproportionately to the lbs. of fuel consumed? That is,
> the actual level in the fuel tank goes down literally more
> slowly from full tank to half, because the gasoline in the
> tank is simultaneously expanding (due to temperature
> increases). By the time the driver reaches a half tank or
> so, the gasoline isn't expanding as quickly, because its
> temperature is pretty constant.
>
> I recall times in the summer where my Civic has achieved
> nearly 300 miles by the time the gage reads half full. Then
> it drops very quickly. In winter, I can't get anywhere near
> as many miles on the trip odometer by the time the tank is
> half full. Still great mileage; just totally out of whack
> with the fuel gage.
>
> Anyone else notice this? Comments on this theory?
>
>
It seems plausible. The volumetric coefficient of expansion of gasoline is
about 0.1% per degree C (http://tinyurl.com/bpp2k) and the constant
circulation of the fuel through the engine compartment (through the fuel
pressure regulator) and warming by the in-tank pump could plausibly add 30
degrees C or more to cold fuel within an hour or two. That would expand 10
gallons to about 10.3 gallons, so if you've only burned a gallon or two in
that time it could appear as a noticable increase in fuel efficiency. If
there is less fuel in the tank, the same amount of heat will warm the fuel
faster.

Maybe the fuel guage reads slightly higher as the passenger compartment
warms up?

Mike

 

Michael Pardee wrote:
> >
> It seems plausible. The volumetric coefficient of expansion of gasoline is
> about 0.1% per degree C (http://tinyurl.com/bpp2k) and the constant
> circulation of the fuel through the engine compartment (through the fuel
> pressure regulator) and warming by the in-tank pump could plausibly add 30
> degrees C or more to cold fuel within an hour or two. That would expand 10
> gallons to about 10.3 gallons, so if you've only burned a gallon or two in
> that time it could appear as a noticable increase in fuel efficiency. If
> there is less fuel in the tank, the same amount of heat will warm the fuel
> faster.
>
> Maybe the fuel guage reads slightly higher as the passenger compartment
> warms up?
>

(hey Mike - it has been a while since we've been in the same thread.
How's things?)

That expansion of gasoline is kind of interesting, if you think about
it:
It really means that fuel should be sold by volume and temperature if
things were fair, huh?
There really should be an adjustment of price at the pump, taking tank
and outside temperature into account - a multiplier of the gas price.

We know the oil companies are not dishonest, (can't get my eyeballs to
roll down for some reason now but let's suppose they are totally
evil, it would be in their interest to heat the fuel before they sell
it to us.
If they heat it just one degree above ambient, it would be a totally
legal way of them making giving you 0.999 gallons for the price of 1
gallon.
So in winter you're really getting ripped of a little, the buried gas
station tank being warmer than your car tank. By the time you've been
driving in the cold for a while, that gallon is really not a gallon
anymore.

Just a thought - maybe a silly one but it does make me go
"mmmmmmmmmmm..."
You guys better be happy I am on the right side of evil here

Remco

 

"Michael Pardee" <michaeltnull@cybertrails.com> wrote
snip
> It seems plausible. The volumetric coefficient of
expansion of gasoline is
> about 0.1% per degree C (http://tinyurl.com/bpp2k) and the
constant
> circulation of the fuel through the engine compartment
(through the fuel
> pressure regulator) and warming by the in-tank pump could
plausibly add 30
> degrees C or more to cold fuel within an hour or two. That
would expand 10
> gallons to about 10.3 gallons, so if you've only burned a
gallon or two in
> that time it could appear as a noticable increase in fuel
efficiency.

Thanks for the numbers. They are not as impressive as I
would have hoped, given the difference I seem to detect. I
believe I see around 30-50 miles difference to get from full
to a half-tank, from summer to winter. The roughly 0.3
gallons might account for maybe 12 miles of this. (My 91
Civic gets about 40 mpg and holds about 11+ gallons, though
these days I rarely let the car empty more than about 9.5
gallons between fillups.)

I am also not sure how or whether the non-uniform shape of
the tank figures into this.

 

Elle wrote:
> "Michael Pardee" <michaeltnull@cybertrails.com> wrote
> snip
> > It seems plausible. The volumetric coefficient of
> expansion of gasoline is
> > about 0.1% per degree C (http://tinyurl.com/bpp2k) and the
> constant
> > circulation of the fuel through the engine compartment
> (through the fuel
> > pressure regulator) and warming by the in-tank pump could
> plausibly add 30
> > degrees C or more to cold fuel within an hour or two. That
> would expand 10
> > gallons to about 10.3 gallons, so if you've only burned a
> gallon or two in
> > that time it could appear as a noticable increase in fuel
> efficiency.
>
> Thanks for the numbers. They are not as impressive as I
> would have hoped, given the difference I seem to detect. I
> believe I see around 30-50 miles difference to get from full
> to a half-tank, from summer to winter. The roughly 0.3
> gallons might account for maybe 12 miles of this. (My 91
> Civic gets about 40 mpg and holds about 11+ gallons, though
> these days I rarely let the car empty more than about 9.5
> gallons between fillups.)
>
> I am also not sure how or whether the non-uniform shape of
> the tank figures into this.

I think it is a very interesting question you've asked. This is a great
discussion.

One would imagine that all these errors accumulate (expansion, fuel
indicator) so maybe with all errors added in you'll see that 30-50
miles discrepancy.
The only way to know for sure is to gather imperical, recording mileage
and gallons because you don't know if you can trust your gauge. It
would at least eliminate it as a variable and possibly accuse it.

Non-uniformity of the tank just tends to make the error worse as they
don't linearize the indicator very well. Of course, the tank shape is
the same in winter/summer. The way they approximate the linearity
probably walks with temperature, so there's most likely another small
error.

Of course - not to give anyone mental whiplash - it could also be that
the car just runs richer in winter for whatever reason..

 

Waiving the right to remain silent, "Elle"
<honda.lioness@earthlink.net> said:

> Thanks for the numbers. They are not as impressive as I
> would have hoped, given the difference I seem to detect. I
> believe I see around 30-50 miles difference to get from full
> to a half-tank, from summer to winter. The roughly 0.3
> gallons might account for maybe 12 miles of this. (My 91
> Civic gets about 40 mpg and holds about 11+ gallons, though
> these days I rarely let the car empty more than about 9.5
> gallons between fillups.)

In summer and winter, you are buying different blends of gasoline.
That cold easily accont for the change in mileage.

Also... You should never use the fuel gauge to calculate mileage.

Fill up the tank and zero your trip odometer. Drive until you have
about 1/4 tank remaining. Fill up, then calculate mileage based on
actual miles driven. Do this several times and take an average.

--
Larry J. - Remove spamtrap in ALLCAPS to e-mail

"I've come here to enjoy nature. Don't talk to me
about the environment!" - 'Denny Crane'

 

"Remco" <whybcuz@yahoo.com> wrote
snip
> One would imagine that all these errors accumulate
(expansion, fuel
> indicator) so maybe with all errors added in you'll see
that 30-50
> miles discrepancy.

I agree, so far.

> The only way to know for sure is to gather imperical,
recording mileage
> and gallons because you don't know if you can trust your
gauge. It
> would at least eliminate it as a variable and possibly
accuse it.

I think we're having a miscommunication. What I'm
challenging here is whether the gage reads more
proportionally to the actual weight of fuel in the tank in
the winter rather than summer. E.g. in winter, I get about
220 miles by the time the gage indicates half-full. In
summer, by contrast, I get about 270 miles.

Roughly.

> Non-uniformity of the tank just tends to make the error
worse as they
> don't linearize the indicator very well. Of course, the
tank shape is
> the same in winter/summer. The way they approximate the
linearity
> probably walks with temperature, so there's most likely
another small
> error.
>
> Of course - not to give anyone mental whiplash - it could
also be that
> the car just runs richer in winter for whatever reason..

Right.

It's not something I'm losing sleep over. Just something
that might be worth mentioning when people come here
complaining that their fuel gage doesn't read in much
proportion to the fuel in the tank.

 

"Larry J." <usenet2@DE.LETE.THISljvideo.com> wrote
> Waiving the right to remain silent, "Elle"
> <honda.lioness@earthlink.net> said:
>
> > Thanks for the numbers. They are not as impressive as I
> > would have hoped, given the difference I seem to detect.
I
> > believe I see around 30-50 miles difference to get from
full
> > to a half-tank, from summer to winter. The roughly 0.3
> > gallons might account for maybe 12 miles of this. (My 91
> > Civic gets about 40 mpg and holds about 11+ gallons,
though
> > these days I rarely let the car empty more than about
9.5
> > gallons between fillups.)
>
> In summer and winter, you are buying different blends of
gasoline.
> That cold easily accont for the change in mileage.

Not in my neck of the woods.

In some parts of the country, yes, there is a significant
difference in gasoline "blends."

> Also... You should never use the fuel gauge to calculate
mileage.

Oy.

We're having a miscommunication.

> Fill up the tank and zero your trip odometer. Drive until
you have
> about 1/4 tank remaining. Fill up, then calculate mileage
based on
> actual miles driven. Do this several times and take an
average.

That's exactly what I do.

 

Elle wrote:
> Oy.
>
> We're having a miscommunication.
>
>> Fill up the tank and zero your trip odometer. Drive until
> you have
>> about 1/4 tank remaining. Fill up, then calculate mileage
> based on
>> actual miles driven. Do this several times and take an
> average.
>
> That's exactly what I do.

thats what i do, too. i also knew on my last trip to laughlin that i can
usually make it there on a tank of gas.

almost all the way there, gauge is reading low. trip odometer says
something like 285 miles. 11.9 gal tank, i usually get 32mpg. (380 to
a tank?)

 

Waiving the right to remain silent, SoCalMike
<Mikein562athotmail@hotmail.com> said:

> Elle wrote:
>> Oy.
>>
>> We're having a miscommunication.
>>
>>> Fill up the tank and zero your trip odometer. Drive until you
>>> have about 1/4 tank remaining. Fill up, then calculate
>>> mileage based on actual miles driven. Do this several times
>>> and take an average.
>>
>> That's exactly what I do.
>
> thats what i do, too. i also knew on my last trip to laughlin
> that i can usually make it there on a tank of gas.
>
> almost all the way there, gauge is reading low. trip odometer
> says something like 285 miles. 11.9 gal tank, i usually get
> 32mpg. (380 to a tank?)

So, how many gallons did you use for 285 miles..?

--
Larry J. - Remove spamtrap in ALLCAPS to e-mail

"I've come here to enjoy nature. Don't talk to me
about the environment!" - 'Denny Crane'

 

Larry J. wrote:
> Waiving the right to remain silent, SoCalMike
> <Mikein562athotmail@hotmail.com> said:
>
> > Elle wrote:
> >> Oy.
> >>
> >> We're having a miscommunication.
> >>
> >>> Fill up the tank and zero your trip odometer. Drive until you
> >>> have about 1/4 tank remaining. Fill up, then calculate
> >>> mileage based on actual miles driven. Do this several times
> >>> and take an average.
> >>
> >> That's exactly what I do.
> >
> > thats what i do, too. i also knew on my last trip to laughlin
> > that i can usually make it there on a tank of gas.
> >
> > almost all the way there, gauge is reading low. trip odometer
> > says something like 285 miles. 11.9 gal tank, i usually get
> > 32mpg. (380 to a tank?)
>
> So, how many gallons did you use for 285 miles..?
>

Exactly - that's the interesting part.

 

Remco wrote:
> Larry J. wrote:
>> Waiving the right to remain silent, SoCalMike
>> <Mikein562athotmail@hotmail.com> said:
>>
>>> Elle wrote:
>>>> Oy.
>>>>
>>>> We're having a miscommunication.
>>>>
>>>>> Fill up the tank and zero your trip odometer. Drive until you
>>>>> have about 1/4 tank remaining. Fill up, then calculate
>>>>> mileage based on actual miles driven. Do this several times
>>>>> and take an average.
>>>> That's exactly what I do.
>>> thats what i do, too. i also knew on my last trip to laughlin
>>> that i can usually make it there on a tank of gas.
>>>
>>> almost all the way there, gauge is reading low. trip odometer
>>> says something like 285 miles. 11.9 gal tank, i usually get
>>> 32mpg. (380 to a tank?)
>> So, how many gallons did you use for 285 miles..?
>>
>
> Exactly - that's the interesting part.
>
i ferget. turned out to be something like 25mpg. incredibly low, but
thats running close to 100 at times, with the A/C, and in 3rd or 4th
gear. definate mileage killers!

 

| Still great mileage
Impossible w-o changing your exhaust*manifold & spark cables.

Honda fits only short branch ( 4 into 1 pipe ), cheap & heavy cast iron
* for its engines <2.2 litre, even a F22A's *'s twin pipes are short.
Result is lower though adequate torque @ low rpm ( as during
buyers' test drives ), but very low ( <½ as much ) torque & mpg @ high
( >3000 ) rpm, this inadequacy expands with rpm.
http://circletrack.com/techarticles/73598
In 6-02 I saw a new Civic vtec 1.6 litre engine with very short * : a waste
of vtec ( no way is torque / mpg esp @ high rpm maximised ).
www.turborick.com/gsxr1127/gasoline.html para 10.2(1) indicates how
bad a civic's * is. Many car makers ( incl Nissan in Sunny 130Y, Hyundai
in Sonata 2.4, Proton in Waja 1.8 ) save on *, because 99.99% buyers
don't test drive on highways, or know / experienced a difference between
short & long branch *.
My F20A had crude carbon-core cables made by Sumitomo, efficiency
was low ( even by 1990 std ) : longest cable has 12.7k ohm, this is why
honda prescribes just 1mm plug gaps.
www.magnecor.com/magnecor1/truth.htm I've changed my F20A's spark
cables 4x, present set ( German cables ) has just 0.2 ohm/ ft : when
warm & w-o load, my F20A can idle @ just 600 rpm, with load ( gear &
brake engaged ) then 550 rpm ( without shaking / stalling ). Plug gaps are
2mm. All these are impossible with crude carbon-core cables, this is
why honda prescribes 770±50 i.e. minimum 720rpm. How low can your
original spec engine ( with crude carbon-core cables ) likewise idle @ ?
Carbon can absorb RFI, but cannot conduct as well as metal : high
efficiency cables makers coil metal wires around carbon cores, then use
these coiled wires to conduct : spark size Ø expands from ½ to 3 mm,
10x brighter, colour turns fr deep to bright blue, 5x as loud.( in open air ).
@ high rpm, any engine ( incl yours ) with 1 small coil & crude carbon-
core cables will have very small sparks, low torque & loud exhaust noise,
this inadequacy expands with rpm.