91 Octane: hard to find in US?

[Jim Stewart]

I don't think the 76 100 octane gas is any kind of traditionally
distilled fuel. One of the places selling it mention that it's made
of "essentially pure components". It sounds like they're blending
relatively pure hydrocarbons. Apparently this stuff burns faster and
is more volatile than normal gasoline. I've heard that some types of
high octane racing fuels burn faster, which is counterintuitive. Most
people seem to associate "higher octane" with "slower burning".

Apparently 100 octane is the most you can get that's street legal.
All the higher octane unleaded doesn't seem to meet reformulated
gas standards or maybe don't have the additive package needed.

Well, just on the face of it, pure iso-octane
has an octane rating of 100. I guess it could
just be that.

 

[y_p_w]

y_p_w wrote:

Well, just on the face of it, pure iso-octane
has an octane rating of 100. I guess it could
just be that.

I saw a couple of spec sheets that said the 76 100 octane unleaded
was 106 RON and 94 MON. I believe pure iso-octane would be 100 each.

<http://www.osbornauto.com/racing/unleaded.htm>
<http://www.leesracing.com/fuelspec/g1.pdf>

It seems to be have been sold under a variety of names, including
"76 100 Octane", "76 Cool Blue 100 Octane", etc. The following lists
"100 Octane Unleaded Racing Fuel" by ConocoPhillips as an EPA
registered fuel:

<http://www.epa.gov/OMSWWW/regs/fuels/additive/web-fuel.pdf>

 

[JD]

Andrew Webber wrote:

I was in the US last month and most stations were 87, 89, and 93.
So
I put in 93. Was that the right decision? Sunoco had 87, 89, 91
and
93 (I think) so I used 91. It was only 2c/gal cheaper than 93, so
if
there wasn't a convenient Sunoco I just used 93 from someone else.

How come 91 is so hard to find? And what do American XT owners do,
put in 93? Should I look for something higher than 91 myself when
I'm
at home?

If you seek out 93 when your car calls for 91, your probably wasting
money.

I'm in New York, and I can't find 91 except from Sunoco, so I just put
93 in most of the time. At these lower altitudes, better to run the
higher octane. Another alternative is to run a tank of 93 down to
half and then top up with 89, but that's a pain.

Too much work, I'll just use 93. Does anyone know why there's so much
93 around, at the cost of 91? Are there that many vehicles that
require it?

=aw
andrew [(e-mail address removed)]

Different additives. 93 is very expensive to make in Canada since the
additives the Americans use is not allowed up here. So it doesn't cost
very much more to make 93 than it does to make 91 in the US. And,
people will generally buy more of a higher octane fuel even though it
doesn't do anything unless the car is tuned to use it; like forced-
induction cars.

I don't know if it's really about "additives" per se. It's all
about the distillation process and the proportion of higher octane
hydrocarbons that ends up in the final product. There isn't going
to be anything in 93 octane unleaded that isn't in 91 octane fuel.

In modern fuels, the octane rating is really AKI (anti-knock index); the
fuel's resistance to detonation. The way they do that is by a process of
oxygenation. This gives it an equivalent rating to some percentage of
octane (the hydrocarbon). Its how they get octane ratings above 100 (which
is equivalent to 100% octane in the fuel). The oxygenation additives they
use in the US are not legal in Canada. The additive we use in Canada are
very much more expensive. So, while there is nothing in 93 that isn't in
91, there is a lot more of it and it drives the price up.

 

[JD]

I don't think the 76 100 octane gas is any kind of traditionally
distilled fuel. One of the places selling it mention that it's made
of "essentially pure components". It sounds like they're blending
relatively pure hydrocarbons. Apparently this stuff burns faster and
is more volatile than normal gasoline. I've heard that some types of
high octane racing fuels burn faster, which is counterintuitive. Most
people seem to associate "higher octane" with "slower burning".

Its not slower burning, it simply resists detonation on compression. Once
burning, high octane burns just as fast as lower octane fuels

 

[Danny Russell]

In modern fuels, the octane rating is really AKI (anti-knock index); the
fuel's resistance to detonation. The way they do that is by a process of
oxygenation. This gives it an equivalent rating to some percentage of
octane (the hydrocarbon). Its how they get octane ratings above 100 (which
is equivalent to 100% octane in the fuel). The oxygenation additives they
use in the US are not legal in Canada. The additive we use in Canada are
very much more expensive. So, while there is nothing in 93 that isn't in
91, there is a lot more of it and it drives the price up.

I'm not a fuel expurt so don't sue me but:

When lead was phased-out of US gasoline ('73-'75), MMT
(methylcyclopentadienal,manganese,tricarbonal) took it's place as the primary octane-boosting
additive. MMT has since been phased-out in the US but is still used in Canadian gasoline.

MMT has a nasty habit of growing rusty red deposits on your plugs and when used in sufficient
quantities can cause fouling. Some OTC octane-boosters in in can are loaded with MMT. It's every
bit as toxic as lead.

US gasoline has been leaning towards achieving the higher octane numbers by blending-in aromatics
(xylene, toluene, etc.) The oxygenating components (MTBE, ethanol, methanol) have secondary effects
of increasing octane and lowering the specific energy content. -Danny

 

[y_p_w]

In modern fuels, the octane rating is really AKI (anti-knock index); the
fuel's resistance to detonation. The way they do that is by a process of
oxygenation. This gives it an equivalent rating to some percentage of
octane (the hydrocarbon). Its how they get octane ratings above 100 (which
is equivalent to 100% octane in the fuel). The oxygenation additives they
use in the US are not legal in Canada. The additive we use in Canada are
very much more expensive. So, while there is nothing in 93 that isn't in
91, there is a lot more of it and it drives the price up.

BTW - AKI is the same as (R+M)/2.

You made it sound like 93 octane fuel would have to be astronomically
expensive in Canadian. Perhaps marginally more, but not 2-3X times
the price like racing fuels. If oxygenates are needed to boost the
octane rating, ethanol is legal and used in Canada. 93 octane fuel
could also be made without oxygenates. If there's any reason why
you can find 93 octane in the NE US and not in Canada, it's more
likely than not a business decision. When the pumps in California's
major brand name gas stations went from 92 to 91, it was also a
marketing decision.

<http://oee.nrcan.gc.ca/publications/infosource/pub/vehiclefuels/ethanol/M92_257_2003.cfm>

I'm guessing the "additive" you're referring to is MTBE, which was
supposed to have been phased out in California by 2002. The deadline
was extended to 2003. The spec sheets I saw for the 100 octane 76
racing gas says it contains MTBE. I don't know if any equivalent
product uses MTBE. Possibly not. I think the petroleum companies
liked using MTBE in fuel because it's a byproduct of refining.
Blending it in fuel was an easy way to get rid of it.

 

[y_p_w]

It won't. If you check your owner's manual, it probably says "91 AKI
minimum". There is a slight difference in fuel economy south of the border
since they use different additives in the gas than we do in Canada.

93 octane "super premium" is recommended for the WRX STi.

 

[y_p_w]

Up here the difference is about 10c-11c Canadian between 87 and 91.
In Ottawa the big sign is typically only for 87 but if it says "88.4"
I would expect 91 to be 98 or 99c (per L).

I don't have the receipts handy, but after being annoyed at paying a
premium for 93 at various stations on my drive to PHL, when I finally
hit a Sunoco and seeing 91, I recall it being only 2c/gal difference.
I'll check when I can, it may have been 2c/L or about 8c/gal.

Thanks everyone for the advice! On this next trip I'll buy 91 at
Sunoco when I can, but won't make any detours looking for it.

There are all sorts of strange marketing decisions in play. A few
years back, all the name brand premium pumps were relabelled as 91
octane (R+M)/2 when they had traditionally been 92 for as long as
I remember. There were article about "Where did the octane go?"
It was a marketing decision that gave the producers more freedom
to make higher octane products with what they didn't divert to the
premium fuel production. It might also have given them an easier
way to make fuel without oxygenates if the need arose.

Back in the 80's, Unocal 76 (before Tosco) sold an 89 octane unleaded
in California competetively priced with other brands of 87 octane
unleaded regular. They didn't carry 87 octane unleaded. They had
a 92 octane premium, and some stations even had "Super Leaded".

 

[y_p_w]

There are all sorts of strange marketing decisions in play. A few
years back, all the name brand premium pumps were relabelled as 91
octane (R+M)/2 when they had traditionally been 92 for as long as
I remember. There were article about "Where did the octane go?"
It was a marketing decision that gave the producers more freedom
to make higher octane products with what they didn't divert to the
premium fuel production. It might also have given them an easier
way to make fuel without oxygenates if the need arose.

Y'now what? I forgot to add, "in California.....".

 

[Andrew Webber]

If there's any reason why
you can find 93 octane in the NE US and not in Canada, it's more
likely than not a business decision.

This discussion is fascinating, thanks!

I should clarify that while 87-89-91 is the standard at most stations,
Sunoco sells four grades, going up to 94 I think. In fact 91 isn't
one of them, maybe it's 87-89.5-92-94? Not sure. Since it would
require driving up to the pump (recall that the stations here only
post 87 prices on the big sign), I've never compared 91 at
Petro-Canada to Sunoco's 92 (or whatever my Forester's minimum would
be) to see if there's a significant price differential. Now I'll have
to, I guess.

And there's another brand with a "Magnum" gas that's either 94 or 96,
I don't remember.


andrew [(e-mail address removed)]

 

[y_p_w]

This discussion is fascinating, thanks!

I should clarify that while 87-89-91 is the standard at most stations,
Sunoco sells four grades, going up to 94 I think. In fact 91 isn't
one of them, maybe it's 87-89.5-92-94? Not sure. Since it would
require driving up to the pump (recall that the stations here only
post 87 prices on the big sign), I've never compared 91 at
Petro-Canada to Sunoco's 92 (or whatever my Forester's minimum would
be) to see if there's a significant price differential. Now I'll have
to, I guess.

I've never seen 94 (R+M)/2 octane on a pump before. I'm curious as to
what WRX STi owners make do with in Northern California - 93 octane
"super premium" is recommended.

87-89-91 is what we currently see in California. Used to be 87-89-92
as far as 2001. Apparently it was a choice of the oil marketers.
Here's an article on the subject:

<http://www.sportcompactcarweb.com/editors/technobabble/0102scc_technobabble/>

This is the interesting part, and it involves some math:

"The crude oil being used and little else determine the amount of
each blend stock available for mixing. Generally, if you just dump
all the blend stocks into a bucket, you end up with something around
88 or 89 octane. If you're selective and only mix the good stuff,
you can make 92, 93 or even 95 octane. But once you take out the
good stuff, you're left with crap--something like 85 octane. Then
you have to leave enough good stuff in the bucket to bring this
pee-water up to at least 87 octane. This limits the amount of 95-
octane gas you can make. If you make 93-octane premium instead, you
use up less of the high-octane stocks, allowing you to make a higher
proportion of premium fuel."

** end quote **

So basically, they want to be able to blend what they've got into
enough "buckets" to meet the demand for premium, mid-grade, and
regular. A 92 octane premium meant they had to divert more of the
higher octane blend stocks to premium, and might have eventually
had excess lower octane blend stocks that they didn't have enough
higher octane stuff to turn into 87 octane regular. So the answer
was to lower "premium" to 91 octane and save some of the higher
octane stuff to being the "pee-water" up to "regular" octane.

BTW - most of the off the shelf "octane boosters" aren't worth it.
If it claims that it can boost the octane rating "up to 10 points",
read the fine print that says that 1 point = 0.1 octane rating.

 

[k. ote]

I've never seen 94 (R+M)/2 octane on a pump before. I'm curious as to
what WRX STi owners make do with in Northern California - 93 octane
"super premium" is recommended.

Octane booster.

BTW - most of the off the shelf "octane boosters" aren't worth it.
If it claims that it can boost the octane rating "up to 10 points",
read the fine print that says that 1 point = 0.1 octane rating.

And yet, a few bottles per fill-up might just be necessary if you're in an
area where there's only 91/92 octane available.

 

[y_p_w]

Octane booster.


And yet, a few bottles per fill-up might just be necessary if you're
in an area where there's only 91/92 octane available.

The jist is that many of these things are a high octane blend of one
or more solvents. The "up to" probably refers to more "points" boosted
if you're starting off with lower octane. Let's say this stuff is
xylene (I've heard some of it is) with an (R+M)/2 octane rating of
116. Add that 16 oz bottle to 10 gallons, you get the following
assuming linear blending of octane rating:

85 octane -> 85.38
87 octane -> 87.36
91 octane -> 91.32
100 octane -> 100.19

Some of these aftermarket additives contain MMT. There's only so
much that can be in your fuel before it starts having a detrimental
effect of your fuel system. There might already be some in the
pump gas. Berryman has a line of octane boosters, and the one that
boosts more octane isn't recommended for any cars with oxygen sensors
or catalytic convertors.

<http://b12chemtool.com/Default.aspx?tabid=141>

 

[Danny Russell]

I don't think the 76 100 octane gas is any kind of traditionally
distilled fuel. One of the places selling it mention that it's made
of "essentially pure components". It sounds like they're blending
relatively pure hydrocarbons. Apparently this stuff burns faster and
is more volatile than normal gasoline. I've heard that some types of
high octane racing fuels burn faster, which is counterintuitive. Most
people seem to associate "higher octane" with "slower burning".

Apparently 100 octane is the most you can get that's street legal.
All the higher octane unleaded doesn't seem to meet reformulated
gas standards or maybe don't have the additive package needed.

We used to have some leaded race fuel available to the "cruisers" here in the Detroit Metro Area
called "Turbo Blue" that was listed as R+M/2 = 104. Just a little bit in the palm of your hand
would evaporate coldly & quickly not unlike a solvent ...even had a bit of a sweet ketone smell to
it or something.

Aside from the good octane number, it ran really crisp in "cammy" motors that normally tended to
stumble and hesitate on the standard-fare premium no-lead. It had really good vaporization in the
intake manifold or something. I haven't seen it in a while.

 

[Moon Guy]

And, people will
generally buy more of a higher octane fuel even though it doesn't do
anything unless the car is tuned to use it; like forced-induction cars.

Moving up one octane grade (about 2 pts.) shouldn't cause trouble,
although using the recommended octane is recommended.
If your vehicle requires a higher octane than recommended, it has a
problem. Either a timing error or cylinder deposits.

A few times a station was out of the 87 octane my car requires, I
refused the 93 octane they offered me at the same price. Operator
thought I was silly, they just showed their ignorance of octane.

Since 1989 I've had perfect success with Chevron, no injector cleaning
ever required over many miles.
I moved to Chevron at Chryslers suggestion after Shell's additive for
leaded fuel requiring vehicles fouled up my '87 vehicle's throttle
barrel injector twice. There was a problem with Shell's additive in our
winter climate which results in water in the fuel. Most Shell stations
here shut down after their serious additive error.

 

[Andrew Webber]

I guess it's worth watching for Sunoco stations then, my trip last
month was from Montreal to Philadelphia, the difference was only about
2c/gal for 91 vs. 93 when I could find it, so I could easily burn as
much as I save if I have to go out of my way.

Next trip is Montreal to Arlington VA, I'll stick with 93 unless I
stumble on a Sunoco.

Thanks for the real-life feedback.

I don't have the details in front of me, but there was consistently a
9c-10c difference between grades, which at most stations was 87-89-93.

At Sunoco with four grades, it was typically 87-89-91-93, with the 93
being 10c more than 89, as normal, and 91 being 1c or 2c less than 93
(it was 1c less in Plattsburgh on the way down, and 2c less in Albany
on the way home). Encountered one full-serve Sunoco on the NJ
turnpike with 87-89-93-94, I took 93 but did see a Porsche Turbo
filling up with 94.

=aw
andrew [(e-mail address removed)]

 

[Moon Guy]

At Sunoco with four grades, it was typically 87-89-91-93,

Most NA vehicles with the base engine take 87 octane- Chrysler 2.7L V6.
The slightly hopped up engines take 89 octane- Chrysler 3.5L V6.
I believe Volvos take at least 91 octane.

My wife's Sybring 2.7L V6 takes 87 octane for 200HP giving very good
acceleration in that car.
Her brother's Volvo 60, 2.4L with turbo takes 91 octane for slightly
over 200HP giving similar acceleration and fuel mileage, but 91 octane
is 15 to 20% more expensive than 87 here.

European cars suffer from tax laws based on engine displacement, so they
build smaller engines and hop them up more.

 

[k. ote]

The jist is that many of these things are a high octane blend of one
or more solvents. The "up to" probably refers to more "points" boosted
if you're starting off with lower octane. Let's say this stuff is
xylene (I've heard some of it is) with an (R+M)/2 octane rating of
116. Add that 16 oz bottle to 10 gallons, you get the following
assuming linear blending of octane rating:

85 octane -> 85.38
87 octane -> 87.36
91 octane -> 91.32
100 octane -> 100.19

When they say "points" they're not talking hundredths, they're talking
tenths at a minimum. Also, you're forgetting that a bottle of octane
booster may not act purely in an averaging capacity. A small amount may in
some cases act far beyond what simple averaging would do.

Otherwise, those scientifically empirical tests of octane boosters when the
booster is only in a 16 oz bottle wouldn't increase the octane value by 2-4
actual AKI.

Some of these aftermarket additives contain MMT. There's only so
much that can be in your fuel before it starts having a detrimental
effect of your fuel system. There might already be some in the
pump gas. Berryman has a line of octane boosters, and the one that
boosts more octane isn't recommended for any cars with oxygen sensors
or catalytic convertors.

That's race-track- or offroad-only booster. Unless the government in your
area is braindead, they doesn't allow products like that to be sold at your
average gas station without clear and obvious labelling. The STP additive,
which is what is sold in the Canadian stores I've been to, is clearly
stated to be safe for catalytic converters and oxygen sensors, and contains
no alcohol.

 

[k. ote]

This isn't true. My old 80s boat car, in the final years before I bought my
STi, wouldn't run smoothly on anything but 94 octane. It was old, crappy,
had serious problems: and 94 octane made it run nicer, with less knocking.

Moving up one octane grade (about 2 pts.) shouldn't cause trouble,
although using the recommended octane is recommended.

Recommended by who? Your implication by ommission is that higher octane is
*not* recommended by car manufacturers. I'd love to hear which ones state
that "only octane of this value is recommended. Higher octane is not."

A few times a station was out of the 87 octane my car requires, I
refused the 93 octane they offered me at the same price. Operator
thought I was silly, they just showed their ignorance of octane.

This is the part where you explain how the higher octane is somehow bad for
your car.

 

[y_p_w]

When they say "points" they're not talking hundredths, they're talking
tenths at a minimum. Also, you're forgetting that a bottle of octane
booster may not act purely in an averaging capacity. A small amount may in
some cases act far beyond what simple averaging would do.

I believe that I did mention that the Prestone octane boost products
are labelled as "1 point = 0.1 octane rating number".

Otherwise, those scientifically empirical tests of octane boosters when the
booster is only in a 16 oz bottle wouldn't increase the octane value by 2-4
actual AKI.

Depends on the product. Tetraethyl lead will boost the octane rating
of any gasoline. Its octane boosting capabilities aren't from
"blending octane".

That's race-track- or offroad-only booster. Unless the government in your
area is braindead, they doesn't allow products like that to be sold at your
average gas station without clear and obvious labelling. The STP additive,
which is what is sold in the Canadian stores I've been to, is clearly
stated to be safe for catalytic converters and oxygen sensors, and contains
no alcohol.

My only point was that it's generally less cost effective to spend (in
US dollars) $5 to boost 20 gallons of 91/92 octane than to buy
marginally more expensive 93/94 octane fuel if available. Some people
are even silly enough to use this stuff on regular unleaded when
mid-grade or premium are available.