About 87 vs. 89 Octane Gasoline

[Mike Jung]

Originally posted by Rogue9 in cheap gas "87 octane" thread
actually I notice quite a difference between 87 octane and 89.
of course another difference is I fill up at Mohawk and the 29 has 5% ethanol. (I don't notice anything past that to 94 and 10% ethanol)

engine runs smoother, a bit quieter and idles smoother with 89.
Originally posted by StarFire in cheap gas "87 octane" thread
I know everyone says to use the 87 octane...and I've tried it 8 times now, 2 at 76, 2 at BP, 2 at Sunoco, and 2 at Exxon. Now my question is this...Why every time I put that gas in, will my car have the following "symptoms"?

1. Very hard to start, if it's really cold out, I have not been able to start, just keeps trying to turn over.
2. Acceleration is very slow.
3. Car Idles very poorly, had the car stall on 2 occations (Sunoco & BP gas).

I'm honestly just curious about it, because I know everyone says you can use it no problem, but I always seem to have problems. The next tank of gas I put in is typically 93 and with in about 5 - 10 miles the car runs so much better (like giving a kid a piece of candy when he's hurt, makes him forget all about it). Now my parents have tried this with my sister's GAGT (which both are 2001s only 2 months apart). They have said the very same thing to me, actually came up over dinner cuz my mom said, "Never again will we put the cheap (87 octane gas) in the car, I was at the mall and couldn't get it started.
It took me 5 minutes to start the car and I thought I was going to have to call someone to come pick me up and have the car towed."

I typically run 89+ in the car cuz in my manual it says that the car can run on 87, but could have the problems, in which case a higher octane gas should be used.
So does anyone know why I have so many issues with the 87 octane?!
Like I said, I'm not trying to start flame wars, but I'm just curious what's different with my car (or the gas stations around me) that would cause this.

Thanks!
-=StarFire=-
Not to start flaming wars but for info purposes.

Where I live you have a choose of (up to 10%) ethanol blended gas (by Sunoco) or 'regular' gas (by like Esso).

I filled my dad's car that has a older 3100 series V6 engine (that requires minimum 87 octane like ours) with 87 octane ethanol blended gas by Sunoco once & with that tank of gas:
-the car never started 'properly'
-idled funny
-lacked power
-gas mileage sucked
Let's just say he won't let me anywhere near his car, to fill-up the tank anymore when borrowing his car :rolleyes:

He fills-up with Esso/Cdn Tire (which buys there gas from Esso) non-blended 87 octane gas from now on...even-though it is the dirtiest gas (in terms of sulphur content) available. The car's engine runs better/ok.

Found out later that from reading online that this is a common problem with ethanol blended gasoline (especially with older cars).
The ethanol blended that is used is a natural octane booster (like +2 octane). So some say that the gas companies blend a 85 octane gas with ethanol to equal a final product of 87 octane.
Ethanol doesn't burn the same as gasoline, so that could be causing some problems for some. For example: in the summer time, ethanol blended gas could cause hot re-starting issues if temps are extremely hot.

So some claim that if you use ethanol blended gas: get gas that is a least 2 octanes more than your car's minimum requirements & your car will 'run' better.

I personally like to use Sunoco ethanol blended gas (just I won't get the 87 octane).
Ethanol blended gas here is cleaner burning & contains less sulphur in it (than non-blended gas).

Plus ethanol is a natural anti-freeze & water remover, which is good in the cold winter time.
Which makes it easier to cold start your car in the winter :thumbs:

PS: ethanol blended gas gets worse gas mileage (epecially in the winter time) than non-ethanol blended gas...(my dad did a comparison after reading blended gas was 'cleaner').

[iceman]

Good info Mike :thumbs:

[SikMindz]

Hmmm...I learned something new today!


So there was a reason for ditching classes! :thumbs:

Thanks for the 411 Mike! I'll have to keep that in mind when 89 oct. gas isn't $2.20+!!! :rage:

[Jason E]

Interesting...

Sik,
If I had a dollar for every time I skipped a class to hop on a message board, I never would have needed to go to college...I could retire :D

[adorai]

higher octane != more energy. A higher octane rating actually indicates that the fuel will burn SLOWER. That's why cars with high compression pistons or boost need higher octane gas. There is absolutely no chance your vehicle can benefit from higher octane gas if it was not designed for it, in fact there is a good chance the fuel will not completely burn before the exhaust stroke.

Ethanol blends cause 2 major changes in the gas. First, alcohol has less heat energy than gasoline, so when it combusts it is not nearly as explosive. Second, it has a much lower freezing point, so in the winter your gas won't gel as much, though unleaded gas doesn't gel a whole lot until you get REALLY cold, negative double digits is where you begin having problems.

A vehicle that is designed specifically for ethanol/ethanol blends wouldn't suffer the drawbacks that todays cars have from ethanol, because they would likely run higher compression and have a more advanced timing.

If this was too long for you to read, just remember higher octane in no way means higher performance. Exactly the opposite, in fact.

[SikMindz]

But he never said higher octane was necessarily better. What he stated was that because of the eth/gas mixture of the "cheaper" 87 gas he was mixing it was more like 85 octane; perhaps lending to faltering power in his vehicle. Now along the same lines people claim to be running "better" on 89...if following the same logic above of mixed eth/gas 89 - 2 = 87 the recommended octane for the car correct? :thumbs:

[pdltodamtl]

Some more info and clarifications for you....

The ( Research Octane Number + Motor Octane Number ) divided by two is measured octane. Fuels with an Antiknock index of 87, 89, 91 ( Unleaded), and 88 ( Leaded ) are listed as typical for the US at sea level, however higher altitudes will specify lower octane numbers. ethanol will not dilute the reading. It just will not burn as efficient as non-ethanol mixtures.


Some of whats next add to what was stated earlier, especially about sulfer and octane

4.11) What are the effects of the specified fuel properties?

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4.11.1) Volatility
This affects evaporative emissions and driveability, it is the property that must change with location and season. Fuel for mid-summer Arizona would be difficult to use in mid-winter Alaska. The US is divided into zones, according to altitude and seasonal temperatures, and the fuel volatility is adjusted accordingly. Incorrect fuel may result in difficult starting in cold weather, carburetter icing, vapour lock in hot weather, and crankcase oil dilution. Volatility is controlled by distillation and vapour pressure specifications. The higher boiling fractions of the gasoline have significant effects on the emission levels of undesirable hydrocarbons and aldehydes, and a reduction of 40C in the final boiling point will reduce the levels of benzene, butadiene, formaldehyde and acetaldehyde by 25%, and will reduce HC emissions by 20% [44].


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4.11.2) Combustion Characteristics
As gasolines contain mainly hydrocarbons, the only significant variable between different grades is the octane rating of the fuel, as most other properties are similar. Octane is discussed in detail in Section 6. There are only slight differences in combustion temperatures ( most are around 2000C in isobaric adiabatic combustion [45]). Note that the actual temperature in the combustion chamber is also determined by other factors, such as load and engine design. The addition of oxygenates changes the pre-flame reaction pathways, and also reduces the energy content of the fuel. The levels of oxygen in the fuel is regulated according to regional air quality standards.


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4.11.3) Stability
Motor gasolines may be stored up to six months, consequently they must not form gums which may precipitate. Reactions of the unsaturated HCs may produce gums ( these reactions can be catalysed by metals such as copper ), so antioxidants and metal deactivators are added. Existent Gum is used to measure the gum in the fuel at the time tested, whereas the Oxidation Stability measures the time it takes for the gasoline to break down at 100C with 100psi of oxygen. A 240 minute test period has been found to be sufficient for most storage and distribution systems.

[pdltodamtl]

4.11.4) Corrosiveness
Sulfur in the fuel creates corrosion, and when combusted will form corrosive gases that attack the engine, exhaust and environment. Sulfur also adversely affects the alkyl lead octane response, and will adversely affect exhaust catalysts, but monolithic catalysts will recover when the sulfur content of the fuel is reduced, so sulfur is considered an inhibitor, rather than a catalyst poison. The copper strip corrosion test and the sulfur content specification are used to ensure fuel quality. The copper strip test measures active sulfur, whereas the sulfur content reports the total sulfur present.


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4.12) Are brands different?
Yes. The above specifications are intended to ensure minimal quality standards are maintained, however as well as the fuel hydrocarbons, the manufacturers add their own special ingredients to provide additional benefits. A quality gasoline additive package would include:

Octane-enhancing additives ( improve octane ratings )
Anti-oxidants ( inhibit gum formation, improve stability )
Metal deactivators ( inhibit gum formation, improve stability )
Deposit modifiers ( reduce deposits, spark-plug fouling and preignition )
Surfactants ( prevent icing, improve vaporisation, inhibit deposits, reduce NOx emissions )
Freezing point depressants ( prevent icing )
Corrosion inhibitors ( prevent gasoline corroding storage tanks )
Dyes ( product colour for safety or regulatory purposes ).
During the 1980s significant problems with deposits accumulating on intake valve surfaces occurred as new fuel injection systems were introduced. These intake valve deposits (IVD) were different than the injector deposits, in part because the valve can reach 300C. Engine design changes that prevent deposits usually consist of ensuring the valve is flushed with liquid gasoline, and provision of adequate valve rotation. Gasoline factors that cause deposits are the presence of alcohols or olefins [46]. Gasoline manufacturers now routinely use additives that prevent IVD and also maintain the cleanliness of injectors. These usually include a surfactant and light oil to maintain the wetting of important surfaces. Intake valve deposits have also been shown to have significant adverse effects on emissions [47], and deposit deposit control additives will be required to both reduce emissions and provide clean engine operation [48]. A slighty more detailed description of additives is provided in Section 9.1.
Texaco demonstrated that a well-formulated package could improve fuel economy, reduce NOx emissions, and restore engine performance because, as well as the traditional liquid-phase deposit removal, some additives can work in the vapour phase to remove existing engine deposits without adversely affecting performance ( as happens when water is poured into a running engine to remove carbon deposits :-) )[49]. Chevron have also published data on the effectiveness of their additives [50], and successfully litigated to get Texoco to modify some of their claims [51]. Most suppliers of quality gasolines will formulate similar additives into their products, and cheaper product lines are less like to have such additives added. As different brands of gasoline use different additives and oxygenates, it is probable that important fuel parameters, such as octane distribution, are slightly different, even though the pump octane ratings are the same.

So, if you know your car is well-tuned, and in good condition, but the driveability is pathetic on the correct octane, try another brand. Remember that the composition will change with the season, so if you lose driveability, try yet another brand. As various Clean Air Act changes are introduced over the next few years, gasoline will continue to change.



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4.13) What is a typical composition?
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" etc. etc.. Nothing is further from the truth. The behaviour of manufactured gasolines in octane rating engines can be predicted, using previous octane ratings of special blends intended to determine how a particular refinery stream responds to an octane-enhancing additive. Refiners can design and reconfigure refineries to efficiently produce a wide range of gasolines feedstocks, depending on market and regulatory requirements. There is a worldwide trend to move to unleaded gasolines, followed by the introduction of exhaust catalysts and sophisticated engine management systems.
It is important to note that "oxygenated gasolines" have a hydrocarbon fraction that is not too different to traditional gasolines, but that the hydrocarbon fraction of "reformulated gasolines" ( which also contain oxygenates ) are significantly different to traditional gasolines.

The last 10 years of various compositional changes to gasolines for environmental and health reasons have resulted in fuels that do not follow historical rules, and the regulations mapped out for the next decade also ensure the composition will remain in a state of flux. The reformulated gasoline specifications, especially the 1/Jan/1998 Complex model, will probably introduce major reductions in the distillation range, as well as changing the various limits on composition and emissions.

I'm not going to list all 500+ HCs in gasolines, but the following are representative of the various classes typically present in a gasoline. The numbers after each chemical are:- Research Blending Octane : Motor Blending Octane : Boiling Point (C): Density (g/ml @ 15C) : Minimum Autoignition Temperature (C). It is important to realise that the Blending Octanes are derived from a 20% mix of the HC with a 60:40 iC8:nC7 ( 60 Octane Number ) base fuel, and the extrapolation of this 20% to 100%. These numbers result from API Project 45, and are readily available. As modern refinery streams have higher base octanes, these Blending Octanes are higher than those typically used in modern refineries. For example, modern Blending Octane ratings can be much lower ( toluene = 111RON and 94MON, 2-methyl-2-butene = 113RON and 81MON ), but detailed compilations are difficult to obtain.

The technique for obtaining Blending Octanes is different from rating the pure fuel, which often requires adjustment of the test engine conditions outside the acceptable limits of the rating methods. Generally, the actual octanes of the pure fuel are similar for the alkanes, but are up to 30 octane numbers lower than the API Project 45 Blending Octanes for the aromatics and olefins [52].

A traditional composition I have dreamed up would be like the following, whereas newer oxygenated fuels reduce the aromatics and olefins, narrow the boiling range, and add oxygenates up to about 12-15% to provide the octane. The amount of aromatics in super unleaded fuels will vary greatly from country to country, depending on the configuration of the oil refineries and the use of oxygenates as octane enhancers. The US is reducing the levels of aromatics to 25% or lower for environmental and human health reasons.

Some countries are increasing the level of aromatics to 50% or higher in super unleaded grades, usually to avoid refinery reconfiguration costs or the introduction of oxygenates as they phase out the toxic lead octane enhancers. An upper limit is usually placed on the amount of benzene permitted, as it is known human carcinogen.

[pdltodamtl]

So in general if you car runs crappy after a new fillup, it may not be a bad idea to not use their fuel anymore.


My autos run badly on citgo gas. but chevron and texaco are very good...

[Craig99SE2]

Originally posted by SikMindz
...if following the same logic above of mixed eth/gas 89 - 2 = 87 the recommended octane for the car correct? :thumbs:

EXACTLY! Not sure the exact number, but a few points lower with Ethanol. Actually, cheaper gas companies like Marathon, etc. use "ethanol-based" gas year round because ethanol is cheaper than naturally-refined gasoline. That way, they sell you less "real gas" but yet keep their octane ratings up. I.e. your car suffers in performance if you run 87 ethanol-blend vs. 87 "100% gas".

Speaking of gas octanes ... I use Sunoco 92 with my ASE chip and I STILL have slight detonation! OUCH! I'm empty right now, so I'll refill with 94 and see how this works. If 94 doesn't do it, anybody wanna buy an ASE? ??

[SikMindz]

::tempting::

But I'm a poor college student...some other life, some other time. LoL

Good find pdL!

[AleroUCD]

Originally posted by SikMindz
Hmmm...I learned something new today!


So there was a reason for ditching classes! :thumbs:

Thanks for the 411 Mike! I'll have to keep that in mind when 89 oct. gas isn't $2.20+!!! :rage:

Most CA gas, except maybe Unocal76, still uses MTBE rather than an ethanol blend, so I don't think this is as applicable to us here.

[Filter]

This is all very interesting I will only use 89 Octane Ethanol Blend from Mohawk in my car. My car starts and runs better on it. I've tried Esso and Petro Canada, but my car doesn't start as strong with it. Granted it is winter here so as it said, your car will start better cause it's like an antifreeze. I stay away from Shell and Shell related gas stations because I don't trust them. Mohawk ethonal works wonders for me. It'll be interesting to see how this all works in the summer.

[Slim]

Originally posted by Mike Jung
He fills-up with Esso/Cdn Tire (which buys there gas from Esso) non-blended 87 octane gas from now on...even-though it is the dirtiest gas (in terms of sulphur content) available. The car's engine runs better/ok.

Hey Mike, here's an interesting tidbit of information....

I know someone who works for Imperial Oil and he admits that Esso has some of the dirtiest gas out there. He also told me that each refinery in Ontario has to clean up their gas by 2004. As it stands right now the cleanest -> dirtiest gas (in terms of sulphur) in Ontario goes like this.

1. Sunoco - 180 ppm
2. Shell - 500 ppm
2. Petro Can - 500 ppm
3. Esso - 550 ppm

Now, those stats were as of 2000. From what I remember, all refineries had to be at 180 ppm or below by July of 2002. And from what I recall, all four refineries are there. As it stands right now, Sunoco is still the cleanest, but has the higest ethanol content. The other three are pretty much equal when it comes to sulphur content. So, you can pretty much buy gas at Shell, Petro or Esso and get the same quality.

Edit: I did some research and found the following.....

According to the Sulphur in Gasoline Regulations Act set out by the Canadian government levels of sulphur have to be as follows:

Between July 1, 2002 and December 31, 2004 - 170 ppm
On and after January 1, 2005 - 80 ppm.

Sorry for the long post guys, just thought I'd throw my $0.02 in. (hrmm, I guess that's less than $0.01333 with conversion). :p

[Mike Jung]

Originally posted by Slim25
...As it stands right now the cleanest -> dirtiest gas (in terms of sulphur) in Ontario goes like this.

1. Sunoco - 180 ppm
2. Shell - 500 ppm
2. Petro Can - 500 ppm
3. Esso - 550 ppm

Now, those stats were as of 2000. From what I remember, all refineries had to be at 180 ppm or below by July of 2002. And from what I recall, all four refineries are there. As it stands right now, Sunoco is still the cleanest, but has the higest ethanol content. The other three are pretty much equal when it comes to sulphur content. So, you can pretty much buy gas at Shell, Petro or Esso and get the same quality.

Edit: I did some research and found the following.....

According to the Sulphur in Gasoline Regulations Act set out by the Canadian government levels of sulphur have to be as follows:

Between July 1, 2002 and December 31, 2004 - 170 ppm
On and after January 1, 2005 - 80 ppm...
Info for Canada:

Sulphur content of regular gasoline produced by refineries across the country, 2000 (http://www.cbc.ca/consumers/market/files/cars/lowsulphurgas/table.html)

2001 Average Sulphur Content in Gasoline in parts per million (ppm) (http://www.foecanada.org/cleanair/fuel_2002-05-08.htm)

Sunoco's Ultra 94 contains less than 50 parts per million of sulphur (http://www.sunoco.ca/content.asp?id=125)

"In 1999, the Government of Canada announced regulations requiring the average level of sulphur in gasoline to be reduced to 150 parts per million (ppm) between July 1, 2002 and December 31, 2004 and to be further reduced to an average of 30 ppm as of January 1, 2005."

[Overclock This]

I have tried all the major gas companies from Ontario, Canada

and Sunoco 89 octane makes my car run the best
I have a 3100 (1997 Grand AM GT)

[Weem]

Originally posted by AleroUCD
Most CA gas, except maybe Unocal76, still uses MTBE rather than an ethanol blend, so I don't think this is as applicable to us here.

From what I've heard, MTBE is on its way out nation-wide. It takes some time to phase it out but 17 states, including CA, so far have discontinued (or are on the way to eliminatining) the use of MTBE.

[AleroUCD]

Yep, should be soon now.

[Mike Jung]

http://www.ene.gov.on.ca/envision/air/sig/2004.htm

[Panacea]

MYTH: E-10 makes engines run hotter.

FACT: The ethanol in E-10 Unleaded actually helps keep your engine cooler, since the ethanol in the fuel combusts at a lower temperature. In fact, many high-powered racing engines use pure alcohol for that very reason.

MYTH: E-10 is bad for fuel injectors.

FACT: Ethanol and E-10 Unleaded have never contributed to burning or fouling of port fuel injectors. Some components in gasoline, such as olefins, have been identified as causing deposits that can foul injectors. Because ethanol burns 100% and leaves no residue, it can’t contribute to the formation of deposits. The ethanol in E-10 actually keeps fuel injectors cleaner-helping improve engine performance. It does not increase corrosion, nor will it harm any seals or valves.

MYTH: E-10 causes vapor lock.

FACT: Vapor pressure specifications of gasoline continue to be lowered by state and federal statute, virtually eliminating the vapor lock problems that were reported in the past. The vapor pressure of gasoline is set by state law, and is lower in the spring and summer than in the fall and winter. Vapor lock usually occurs when a winter grade of gasoline formulated for cold weather starts is used under summer-like conditions. (Remember: 90% of E-10 Unleaded is gasoline, so the formulation of the base gasoline has a dramatic effect on performance.) Also, all major auto manufacturers now have in-tank fuel pumps which are not subject to vapor lock like the older in-line fuel pumps.

MYTH: E-10 plugs fuel lines.

FACT: Today occurrences of plugged fuel filters are virtually non-existent. The cleansing nature of E-10 can actually keep your fuel system cleaner and lead to improved performance. In the case of dirty fuel systems, contaminants and residues that have been deposited by previous gasoline fills can be loosened. That residue can get caught in the fuel filter. In older cars, especially those made prior to 1975, replacing the filter solves the problem, and once your fuel system is clean, your car's performance should improve as well.

MYTH: Ethanol reduces gas mileage.

FACT: Many variables affect fuel economy, including seasons, the weather, and the state of your car, road grade, tire pressure, and the use of air conditioners. Most drivers using E10 see an increase or no difference in fuel economy.

MYTH: Most auto mechanics tell people not to use E-10 .

FACT: A mechanic who says not to use E-10 simply does not have correct information—particularly since every major automaker in the world approves the use of E-10. Unfortunately, there has been little information for mechanics on fuel formulation, so when a problem appears to be fuel related, some mechanics will immediately ask if E-10 Unleaded has been used. In some states, E-10 Unleaded advocates have offered a substantial reward to any customer who can document damage from E-10 Unleaded to his or her car—and so far, no one has ever collected.

MYTH: E-10 can’t be used in older cars.

FACT: The formulation of gasoline has changed dramatically over the past few years without affecting the performance of older cars. Many older cars were designed to run on leaded gasoline, with the lead providing necessary octane for performance—and the lead oxides that were formed during combustion provided a cushion that reduced wear on non-case-hardened valve seats. When lead was phased out of gasoline, oil companies added chemicals to raise the octane rating—and other additives to replace the "lubrication" value of lead. The ethanol in E-10 raises octane in gasoline by three points—and it does so using a natural, renewable additive that works well in older engines.

MYTH: E-10 can't be used in small engines.

FACT: E-10 is perfectly acceptable in lawn mowers, snowmobiles, and other small engines. Manufacturers of this equipment know that more than 40% of the gasoline sold across the U.S. contains oxygenates such as ethanol, so they've made certain that their engines perform on these clean-burning fuels. E-10 may be used anywhere that unleaded gasoline is used—from ATVs to chainsaws, from lawn mowers to personal watercraft. Virtually every small engine manufacturer approves the use of E-10 in its equipment.


:)

[atc3434]

higher octane != more energy. A higher octane rating actually indicates that the fuel will burn SLOWER. That's why cars with high compression pistons or boost need higher octane gas. There is absolutely no chance your vehicle can benefit from higher octane gas if it was not designed for it, in fact there is a good chance the fuel will not completely burn before the exhaust stroke.

Ethanol blends cause 2 major changes in the gas. First, alcohol has less heat energy than gasoline, so when it combusts it is not nearly as explosive. Second, it has a much lower freezing point, so in the winter your gas won't gel as much, though unleaded gas doesn't gel a whole lot until you get REALLY cold, negative double digits is where you begin having problems.

A vehicle that is designed specifically for ethanol/ethanol blends wouldn't suffer the drawbacks that todays cars have from ethanol, because they would likely run higher compression and have a more advanced timing.

If this was too long for you to read, just remember higher octane in no way means higher performance. Exactly the opposite, in fact.

Without starting a flaming war, I'd like to disagree with some of what you're saying. I agree that higher octane doesn't offer more performance than lower octane, unless you see detonation with the lower octane. At least with the Grand Am, you'll often see detonation with 87 and even 89 grade, especially in the warmer summer months. This isn't unsubstanciated, I've spent plenty of time scanning for knock and listen for it, and there is quite a difference between 87 and 93 for the 3400. Even before I ran DHP, which has slight more agressive timing, anything less than 91 octane would create knock retard. Knock retard pulls timing, and this will hurt performance. Every degree of ignition advance is worth around 2hp. If you see 5* of timing pulled from knock retard, you'll sacrificing 10hp, which is enough to notice (if you butt dyno is properly calibrated, or you have scan tools. Or both!)

So, to say that higher octane fuel in no way means higher performance is faulty. Your logic about the burn speed and energy of octanes is perfectly logical, but that more stable burn speed prevents power robbing detonation. Can you safely run 87 octane? Sure, I do all the time when I know I'm going to be at low load, cruising applications. But if I'm going to be demanding maximum performance for the 1/4 mile, autox, or Friday nights, I'll fill up with the good stuff, otherwise I'll see substancial knock retard, 5-8*. So, I contest that higher octane does in fact have benifits for the 3400.