Different grades of gas through the same pump hose

[yuba4]

I have a couple of pump questions:

o When you buy gasoline through a pump with one hose that serves three
different grades of gas, is there gas in the hose that you are getting that
might be a different grade? That is, if you are buying premium and the
customer before you bought 87-octane "regular unleaded", is the hose still
filled with 87 so you would get a gallon or so of the wrong fuel grade?

o If you prepay and the pump shuts off, do you get more gas from draining
the hose than you get when you stop the pump from the nozzle handle?

o What is the volume of an average 10' (or whatever length) hose?

Gene

[stu]

You have a valid point but does it really matter? Perhaps you want regular
and the guy before pumped premium or vice versa. Think about all your fill
ups; there is still some residual gas left in your tank from your first fill
up maybe many years ago. So, What...

[George Jefferson]

:You have a valid point but does it really matter?

I've never seen them do that, so i guess it does matter.
(possably just legal problems rather than real issues)

Years ago Sunoco had a system of mixing grades, you could get
economy or premium, or select a couple of mix ratios. They
used a double hose, with the mix done at the nozzle.

[Jeff McDonald]

I shut down the pump and let the hose drain through the open nozzle.
Call me cheap. :)

I saw one Sunoco-like pump where one could pick many grades, but
Super Ultra (or whatever) had its own seperate hose.

Sometimes when you show up at a pump, it's not reset and you can
spot what the last grade purchased was.

Jeff
yuba4 wrote in message <6mpW6.9575$ki5.1...@vixen.cso.uiuc.edu>...

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[billk...@snotmail.com]

In article <6mpW6.9575$ki5.1...@vixen.cso.uiuc.edu>, "yuba4"
<ge...@yubatech.com> wrote:

> I have a couple of pump questions:
>
> o When you buy gasoline through a pump with one hose that serves three
> different grades of gas, is there gas in the hose that you are getting that
> might be a different grade? That is, if you are buying premium and the
> customer before you bought 87-octane "regular unleaded", is the hose still
> filled with 87 so you would get a gallon or so of the wrong fuel grade?

Until last Tue., I was working at a gas station with that type pump.
I had asked that same question to one of the maintenance guys and he
basically shrugged his shoulders and said he didn't know. I guess thats
why he was paid $.50/hr. over minimum wage.

I live in Orygun, and they do test for minimum octane. When they tested
the pumps a couple months ago, their "octane tester" was in for
calibration, so I couldn't see what the procedure/volume used was. I asked
the Dept. of Agriculture guy about the residual fuel in the hose affecting
the octane rating and he said that they "purge" the hose. He did note that
the octane rating listed on the pump is a MINIMUM OCTANE RATING and actual
tested octane tended to be a few .1's higher.

My personal opinion is that if you are buying the premium grades, let your
tank get fairly low and get a fill. If you have a can for lawn mower gas,
fill it first if you are that concerned about getting the max octane. I
guess another option is to fill up after a friend that uses premium.

>
> o If you prepay and the pump shuts off, do you get more gas from draining
> the hose than you get when you stop the pump from the nozzle handle?

I would guess our pumps would dribble about 2-3 oz. if it didn't click off
after reaching the pre-set amount.

> o What is the volume of an average 10' (or whatever length) hose?
>

I personally would estimate about .5 gal of residual fuel left in the hose.

One of the biggest rip off I see is the price charged for Plus. Typically
one will pay for 89.5 octane and only get 89.
At my station, Plus was mixed at the pump using 60% 87 octane and 40% 92 octane.
With 92 being priced at $.20/gal higher than 87, Plus should be only
$.08/gal higher than 87. We charged $.10 more, as most stations in my area
do.

--
To email me, change snot to hot

[TeGGeR]

>
> > o What is the volume of an average 10' (or whatever length) hose?
> >

Assuming a 3/4" ID dia hose, 10' long and completely full, you'd have
53.014 cubic inches, or a cube roughly 3-3/4" per side. There being 231
cubic inches in one US gallon, you'd have about a quart of gas.

--TeGGeR

[George Jefferson]

:> o If you prepay and the pump shuts off, do you get more gas from draining

:> the hose than you get when you stop the pump from the nozzle handle?
:
:I would guess our pumps would dribble about 2-3 oz. if it didn't click off
:after reaching the pre-set amount.

The theory here is that by prepaying, the nozzle is still open
when the pump shuts off, so you might get a little more.
I think in reality the auto shut off nozzle closes so fast when
the pressure drops that you dont get anything for free.
Notice that if one guy had a trick to empty the hose, the
next customer would see a couple of cents ring up filling the hose
before squeezing the nozzle.

I never trusted those mix on the fly arrangements, and I'm sure
I wasn't the only one (see how they all disappeared in the northeast).

[yuba4]

So that answers my question. If there is a valve in the nozzle handle that
shuts off when the pressure drops, then the hose will always be full of gas.
There would be no way to empty the hose. That makes sense.

Thanks for the info...
Gene

" George Jefferson " <gj...@one.net> wrote in message
news:tiksbea...@corp.supernews.com...

[billk...@snotmail.com]

In article <o3uW6.62646$QE4.6...@news20.bellglobal.com>, "TeGGeR"
<teg...@dont.like.spam> wrote:

I haven't paid a lot of attention to other pumps, but on the ones I used,
there is a bit more plumbing than just the hose.
The hose attaches to the very top of the dispensor assembly, but the
mechanical meters etc. are about knee high. Now, what's the ID of the pipe
taking the gas from that point to the top of the dispensor? I never
thought to look when I had the opportunity to do so.

[py...@texas.next]

The dispenser internal piping is usually 3/4" o.d. copper.
From the blending unit (or the check valve if non-blending)
it's about 7' to the hose fitting on a typical overhead
Gilbarco, Wayne-Dresser, Schlumberger, etc.

[py...@texas.next]

Q1: Already answered by Tegger, but here goes:
There are different sizes of hoses. Some are co-axial.
Normal everyday hoses are 5/8" i.d.
Co-axial normal everyday hoses are 0.625" i.d. for the gas flow.

Q2: No. Nozzle shuts off if flow goes to 3 psi or less.

Q3: Use pi x r squared x length to compute volume.
Hoses, whips, breakaways are usually 10'.
Add in ~7' of 3/4" o.d. (~5/8" i.d.) for dispenser interal
piping.

[Milspec4]

>>When you buy gasoline through a pump with one hose that serves three
different grades of gas, is there gas in the hose that you are getting that
might be a different grade?<<

Others have answered the question and calculated the approximate amount. What
is it's significance? There seems to be a perception that all gasolines of one
octane grade are chemically similar, and thus general rules can be promulgated
about "energy content ", "flame speed", "combustion temperature" , "antiknock'
and "preignition". Nothing is further from the truth. The fuel property the
octane ratings measure is the ability of the unburned end-gases to
spontaneously ignite, under the specified test conditions, in a standardized
test engine.

In general, the octane response will be linear for most hydrocarbon and
oxygenated fuels eg. 50:50 of 87 and 91 will give 89; 25:75 gives 90 . Even
at a ratio of 1gal of dilution, of the lower octane, in a total of 10 gals
pumped into the tank, you'd still have a 90.63 POP [pump octane rating]. This
should be negligible for non-racing driving, very difficult to demonstrate as
giving less performance and easily accomodated by the engine management system
on '90s and later cars.

RON [research octane] minus MON [motor octane] gives a figure called
'Sensitivity'. The two test methods use different test conditions, especially
the intake mixture temperatures and engine speeds. Thus, a fuel that is
'sensitive' to changes in operating conditions will have a larger difference
between the two rating methods. Some modern fuels, typically, may have
sensitivities around 10. To reduce this factor, the US 87 Antiknock Index
([RON+MON] / 2 ) of unleaded gasolines is recommended, not mandated, to have at
least an 82 MON, thus lowering the sensitivity of these fuels.

There can be a 'sensitivity' problem for the new, reformulated, low-aromatic
gasolines. MTBE boils at 99*F, whereas ethanol boils at 140.4*F. You might
find worse performance by buying another brand that had a greater 'sensitivity'
although also rated at 91 pump octane; or vice-versa.

If the octane enhancers are distributed differently, throughout the boiling
range of a fuel, then engines can 'knock' on one brand of a specific Pump
Octane Number (RON+MON)/2, but not on another brand of the same PON. The fuel
can segregate in the manifold, with the very volatile fraction reaching the
combustion chamber first and, if that fraction is deficient in octane, then
knock will occur until the less volatile, higher octane fractions arrive. For
example, some drivers have discovered that an 87 (RON+MON)/2 from one brand has
to be substituted with an 89 (RON+MON)/2 of another; and that, because of the
combination of their driving style, engine design, vehicle mass, fuel octane
distribution, fuel volatility, and the octane-enhancers used.

Remember that the Octane Number Requirement (ONR) of an engine varies among
vehicles of the 'identical' model production-run and your individual driving
style. You can experiment, as the variations in vehicle tolerances can mean
that the ONR, for a given vehicle, can range over several Pump Octane Numbers
-- (PON aka [RON+MON] / 2) or the more technical designation, Antiknock Index
[AI]. Car makers have an engine tested for ONR, but not necessarily with the
fuel you are using. The owner's manual rating, for the model, is only a
starting point from which to determine your specific vehicle's ONR as driven by
you with your favorite fuel. The industry believes that most consumers seldom
drive so severely as the testers run the test engines to determine PON.
Therefore, they may be satisfied by a lower pump octane fuel than the test
indicates; providing they're not altering their engine's operating specs.

While there is no direct correlation between antiknock ability and preignition
tendency, high combustion chamber temperatures favor both, and so one may lead
to the other. An engine knocking during high-speed operation will increase in
temperature and that can induce preignition. Conversely any preignition will
result in higher temperatures that may induce knock. If preignition continues,
it can increase in severity and become Runaway Surface Ignition (RSI), thus
melting pistons. Obviously, if prolonged, either condition can cause
significant, engine damage. After-run, some call it dieseling, the continued
irregular combustion after the ignition is turned off, is one obvious sign of
preignition.

If you already are using the proper octane fuel, you will not obtain more power
from higher octane fuels. If you are using a fuel with an octane rating
slightly below the optimum, then using a higher octane fuel will cause the
engine management system to move to the optimum settings, possibly resulting in
both increased power and improved fuel economy. You may be able to change
octanes between seasons, reducing octane in winter, to obtain the most
cost-effective fuel without loss of
driveability.

Today, it is accepted that no one octane rating covers all use and different
brands will have different ONRs for different, specific vehicles and drivers.
You have to find out for yourself by cautious experimentation.