
When Gas Becomes Cheaper, Americans Buy More Expensive Gas - OrwellianChild
http://www.nytimes.com/2015/10/20/upshot/when-gas-becomes-cheaper-americans-buy-more-expensive-gas.html
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unchocked
I have a psychological model for people buying premium gas when they don't
need it, that fits in with the demand for it being quite price-elastic.

Most people don't understand cars very well, but just about everyone
understands that they are complicated and they need maintenance. So there's
always an anxiety that the car is going to break. I think the way we deal with
limited agency in an uncertain environment is to just "do what we can". So
when there's an unexpected windfall at the pump (cheap gas), the maintenance-
anxiety heuristic says "apply it to maintenance" and people buy premium gas.
Because that's good for the car, right? And now they've "done something", so
the anxiety is reduced.

Of course, it doesn't actually have any mechanical benefits, but this isn't a
mechanical issue.

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jackfoxy
News flash: use the octane rating your automobile requires. (period)

Higher octane is for high compression engines. It's a waste of money to use in
in most cars.

~~~
dghughes
You can even use a lower octane than recommended since modern cars with
computers can compensate.

~~~
jacquesm
You're one flaky knock sensor away from a very expensive repair _if_ your car
has a knock sensor. Knocking, aka uncontrolled (usually premature) detonation
can be detected but by then it has already happened and with aluminum pistons
it doesn't take much to blow a hole in them depending on when in the cycle the
fuel detonates. The higher the compression ratio of the engine the earlier in
the cycle this would happen the bigger the chance of a very expensive repair
(if not a write-off...).

Don't use a lower octane than what your manufacturer recommends, that
compensation is there as a safety precaution, not as a means to allow you to
shift the standard octane your engine really needs.

Note that running your engine on fuel with lower octane number than what your
manufacturer recommends is also a way to void your warranty (and since the
damage is quite specific and the evidence is right in your tank there is a
very good chance that will kick in).

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lutorm
This is true, but in practice you are one flaky knock sensor _and a lead foot_
away, because detonation really is only an issue at high power levels. I'd
wager most people don't really ever go full throttle and if they do, for a few
seconds at most, so I suspect the potential for damage is not that great.

If you _habitually_ floor it, though, then yes.

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jacquesm
That's only partially correct. If your engine 'knocks' regularly you're
stressing it in a way that is detrimental to the engine's life-span. If you do
it whilst under high power then the risk of damage increases, but doing it
over a longer period at lower power level is _just_ as damaging (due to the
repeated stressing of the engine materials, specifically the piston heads, the
cylinder walls, the gasket material and the valves as well as the head).

An engine that knocks regularly will die, no matter what the power levels at
which it takes place simply because it isn't designed to deal with that stress
on a regular basis, engines are designed with some leeway but not so much
margin that they could take such abuse and still manage the same life-span
they'd achieve with normal use.

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lutorm
You might be right.

My thinking was this: peak cylinder pressure basically is proportional to
torque, so at lower power levels cylinder pressure is overall lower. Even if
the engine knocks, which will cause a spike in cylinder pressure, it starts
from a much lower baseline, and there's also much less air/fuel mixture in
there. Thus peak cylinder pressure for a knocking engine at low torque may not
be much larger than that of a non-knocking engine at full power. But this is
just speculation on my part, I don't have quantitative data.

It's also possible that it is the sharp pressure spikes that do the damage
rather than the overall pressure level, in which case what I'm saying would be
less applicable.

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gertef
I wonder if these folks are buying higher octane gas than their car needs when
gas is cheap, or buying lower octane gas than their car needs when gas is
pricey.

~~~
eitally
I drive a car that only requires 87. When gas got down to $2.00/gal, I tried
93 for a couple tanks in a row, just to see what it did for mileage/power. The
result: a 4Runner is a big, brick-shaped SUV and will drive like a big, brick-
shaped SUV no matter what gas is in it. I switched back to 87.

~~~
modoc
Lower octane fuel actually has more energy per volume, so if your car's
compression is low enough for 87, using 93 just gives you less power and worse
efficiency.

~~~
outside1234
Also can slowly wreck your engine since it burns hotter.

Use the octane your car was designed for!

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matwood
For my cars I don't care since they go through the gas so quickly. For
lawnmowers and the boat, I only buy the more expensive ethanol free gas.

~~~
cpursley
My father runs a commercial landscaping business. The ethanol laced fuel
wreaks havoc on his fleet of 2 cycle engines.

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toomuchtodo
He hasn't switched to natural gas mowers yet? I've seen them everywhere
lately.

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cpursley
Hum, I might suggest that. Primarily I'm talking about things like leaf
blowers, weed eaters, etc.

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toomuchtodo
I'd highly recommend they look at electric versions of those devices when
possible.

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encoderer
In modern filling stations the pump is able to mix the fuel so tanks for each
individual octane are not necessary.

In older filling stations with a single tank, they solve this by selling
"premium" to everybody, whether or not you select 87 or 92.

Gasoline is usually a loss-leader for filling stations to bring people into
the store, so I suppose it's a negligible impact on margins.

~~~
jonah
I've been wondering how much "pay-at-the-pump" card machines affect sales of
incidentals. If a fraction of customers are going inside and being exposed to
the snacks, how's that work out?

~~~
jacquesm
Badly. Gas stations make a considerable portion of their profits from the
store. If a station does not make enough money on the store it is one bad
season away from being converted to fully automated.

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blinkingled
Doesn't the higher octane gas also have various additives that claim to make
your engine run smoother etc.? I have tried that last time when regular gas
was $1.98 and it did seem to make a difference on a long trip - engine felt
smoother even when I had forgotten that I had fueled it with the higher octane
one.

~~~
saryant
Those are called addpacks, they are unrelated to the octane level. Chevron
Techron, Shell V-Power, etc.

~~~
dredmorbius
Where in the supply chain are they added?

Regionally, virtually all petrol (gasoline) for _all_ fuel companies comes
from the same refinery, with the same treatment.

~~~
saryant
At the station. This is what differentiates branded gas stations as most
aren't even owned by the integrated majors anymore and they aren't required to
buy gasoline from their respective brand parent.

~~~
dredmorbius
Thanks. Yeah, as I commented elsewhere, within regional markets, most fuel is
sourced from the same refinery, and is effectively identical.

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yodon
Every car I've ever owned, I've done the experiment and compared $/mile
(dollars per mile, not per gallon) on premium and regular. Every one of my
cars has had a noticeably lower cost per mile on premium compared to regular
(I'd love to quote the number but it's been around 10 years since I ran the
rest on my current car so all I recall is the outcome). I've encouraged
several friends and family members to run the same experiment, and all
reported the same result. Significantly newer cars with octane sensors might
change this result, but I suspect it holds for most of the used cars on the
market out there, so for at least some of us the more "expensive" gas is
actually the cheaper gas.

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S_A_P
I buy the gas that my car recommends. In my people hauler(we've 7 in the
family) I run 87 octane at the cheapest price feasible. In my commuter car(2.0
turbo) it wants e85 or 91 octane. Texas sells 89 or 93 octane so I buy 93,
with an occasional 89. When I want to get 10% more horsepower for 2/3rds the
fuel economy I buy E85. Price doesn't have any effect on what I purchase. I
think it only would come into play if regular was 1.85 and premium was 4.00.

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ams6110
This describes nobody I know. For my part, I dollar-cost average my gas
purchases. I buy a fixed dollar amount regardless of the price. That way I
automatically buy more when it's cheaper and less when it's expensive.

I do buy premium for my small engines (lawn mower, etc) because (at least in
my area) it's less likely to have ethanol added which is bad for most small
engines.

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lutorm
I wonder if this is purely a result of calling the high-octane gas "premium"
or "super" or whatever. If it was just called "87" and "91", where one doesn't
sound obviously better and more exclusive than the other, I wonder if the
effect would be the same.

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acjohnson55
Wow. I don't think it would ever cross my mind to by higher grade gas, perhaps
at least until it was a literally negligible percentage of income. But even
then...

Who are these people?

~~~
revelation
Germany somewhat recently added a required E10 fuel mix (10% ethanol), cheaper
than normal super, and uptake has been slower than expected (certainly going
by compatible cars).

A lot of people, as it turns out, are not particularly bright.

(Now, ethanol is less energy dense than gasoline; right now the gap is 2 cents
between E10 and E5, so you might make the calculation if you actually get more
energy per buck from E5. It's another story for fuel consumption, though.)

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GauntletWizard
E10 fuel is about 3% [1] less efficient than more pure gasoline, and much
harder on car engines, even ones designed for it (unsourced, but so my
gearhead friends have told me)

So, no, maybe consumers are making the smart choice.

[1]
[http://www.eia.gov/tools/faqs/faq.cfm?id=27&t=10](http://www.eia.gov/tools/faqs/faq.cfm?id=27&t=10)

~~~
revelation
I've mentioned the _theoretical_ energy density, and notice that this is what
the EIA uses to derive the 3% efficiency loss. This is a highly theoretical
value; combustion engines are very complex beasts and theoretical energy
density is a poor predictor of their efficiency, but what is known is that
higher octane ratings are beneficial for fuel efficiency. Since ethanol has a
high (>=100) octane rating, it might actually improve fuel consumption despite
being less energy dense.

Also, E15 and higher fuel blends have been in widespread use in the US for 10+
years now. I don't think car engines die quicker in the US.

~~~
bri3d
[http://feerc.ornl.gov/pdfs/pub_int_blends_rpt1_updated.pdf](http://feerc.ornl.gov/pdfs/pub_int_blends_rpt1_updated.pdf)

Here are some fairly extensive test cycles applied to real-world engines,
which found that the effect closely mirrors the theoretical reduction in
energy density (3-4% for E10, ~7% for E20).

Higher octane ratings are not generally beneficial for fuel efficiency unless
the engine has been designed for them (compression ratio, cam profile, timing,
tune). Dropping higher-octane fuel into an engine designed for a lower-octane
fuel will generally not affect economy.

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Palomides
it seems like this could also be explained by people being more willing to
drive luxury/sports cars when prices for gas are cheaper?

running the incorrect octane is at a minimum bad for your mileage and can also
be damaging to your engine...

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alphonse23
articles like these make me feel like a pawn in a JP Morgan Chase's (ie big
banks) little game.

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gweinberg
The author is a moron. Buying more gas when gas becomes cheaper is exactly
what economic theory predicts.

