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Old 04-23-2009, 10:00 AM   #1
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What will 100 octane gas do?

Forgive me for my ignorance, but I found a gas station selling 100 octane gas (at $5.50 a gallon) I believe primarily used for boats. It is by a lake. My question is, what would happen if I put a tank of that stuff in my car? Just curious more than anything.

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Old 04-23-2009, 10:12 AM   #2
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Personally i would've thought the ECU would adjust the timing to a degree to compensate, just as it would if it were poor quality, thus 'buffering' the potential benefits. The car would have to have a specific 'map' to run on such a high octane fuel from my experience so without it, it would be a waste of money.
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Old 04-23-2009, 10:32 AM   #3
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The ECU will adjust and provide better throttle response and a slight hp gain. Specially with California having only 91 Octane where other states have 93 to 95 octane available. I wouldn't use a tankful of 100 octane but a mixture of 91 and 100 octane to come up with a 93-94 octane mixture. Since you're in Sj you can go to a 76 station located at Almaden Expressway and foxworthy. They have 100 octane available at the pump unleaded.
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Old 04-23-2009, 10:49 AM   #4
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Ah... ok. Someone told me it would be bad since the engine will be running hotter than usual. Yet another person told me higher ocatne = faster car haha!
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Old 04-23-2009, 12:33 PM   #5
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I have used 104+ and several other boosters, most of which I think were toluene based. The biggest difference I notice is how smooth the engine runs and perhaps a smidgen more power, it's worth 6 beans to find out. Beware though, use a funnel, that **************** will eat clear coat like piranha on a chicken leg.
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Old 04-23-2009, 05:09 PM   #6
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I believe it would not do anything bad to your car. Higher grade of fuel is always better. If however you go to lower grade, detonation and preignition may occur. I am not a mechanic so take this lightly.
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Old 04-23-2009, 05:50 PM   #7
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I belive Edvelin dyno'd his car with 100 oct race gas and it netted him about 3 hp.
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Old 04-23-2009, 08:23 PM   #8
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High octane fuel doesn't necessarily burn hotter, it's simply more stable than lower octane fuel. That's why high compression engines (ours) and forced induction engines (turbo charged and supercharged) need high octane.

If you run 87 in the for mentioned engines, without a knock sensor retarding the timing, you'll damage the engine because of pre ignition.

The engine will be livin' the good life on 100, Europe has 98 everywhere and I can't tell you how well 1.1 and 1.8 liter cars run.

P.S. Adam, damn nice car!!
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Old 04-23-2009, 08:59 PM   #9
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Originally Posted by Jaxonalden
The engine will be livin' the good life on 100, Europe has 98 everywhere and I can't tell you how well 1.1 and 1.8 liter cars run.
Minor clarification here: European ratings are RON, not (R+M)/2, as in the U.S. The same gas will always have a higher RON octane rating than a (R+M)/2 rating, since (R+M)/2 is actually (RON+MON)/2. This link explains the difference pretty well: http://www.csgnetwork.com/octaneratecalc.html

To the OP, many OBDI and OBDII cars have a separate "low octane" ECU timing table, so that the car can still run even if some knucklehead puts 87 in the tank by mistake and a certain level of knock is detected. However, I don't know of any manufacturers that build in a third, separate "extra high octane" timing table just on the off chance that an owner might fill 'er up with something higher than 93 octane gas. So unless you have a separate 100-octane program uploaded into your ECU (like the switchable APR program I have in my 2006 VW GTI), the extra octane won't do anything at all, except make your wallet lighter.
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Old 04-23-2009, 09:26 PM   #10
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i used to own a highly modded Volvo S60R. that car LOVED 100 octane. there was a gas station near me that sold it and I would mix in 5 gallons with a tank of 91 to net around 93-95 octane. i would also fill up two 5 gallon cans and keep it in my garage - i was addicted.

i called it "cracktane".

on that car - dyno proven - it was a 30hp gain to run the better gas.

i did my homework. high octane gas does not "make more power" or "have more engergy" the octane is a measure of how stable the gas is. the higher the octane the more precise and reliable the burn is. so the gas will ignite in a more regular / fashion. imagine that each cylinder - every time it fires - if you had to time *exactly* when it's going to pop. the timing of the ignition is timed wiht the piston being at the top of the power stroke.. to be on the safe side, the car delays firing the spark plug until your piston is already going down. in high temps and high pressure situations the gas can preignite and the gas can start to burn too soon - so the car is timed so that the ignition si always when the piston is on it's way down - and you don't get a power stroke from when the piston is trulyl at hte very very top of the power stroke. for hypothethical concerns - imagine that you only had the spark plug fire when the piston was roughly 1/2 way DOWN already.... you only get 1/2 the downward stroke under power.

now imagine you have high quality gas that burns the EXACT same way EVERY time. now the computer/ignition can advance the timing so that the spark plug fires and it's all times EXACTLY so that the piston is JUST starting to go down,a nd then BAM, it fires. yhou get a power stroke that is the entire length of the stroke.

essentially, the higher octane gas is higher quality, more stable, less prone to preignition, and it will burn ina m ore consistent fashion. which makes it easier for the computer/igntion to advance timing and get the most/longest power stroke. crappy gas causes timing to be retared, meaning the car waits for the piston to go down further before it lights the gas...

high octane gas worked magic in my S60R. after running a tank of that stuff in my S60R, driving on 91 was like driving a different car. the car ran much stronger and OMGF the smoothness was incredible. you could feel it was smoother and much more pwoerful. that, ,however, was in a highly boosted car with above stock boost pressures.... high temps, high pressure - it needed high octane. that car was very sensitive to temps and octane.

i have no idea how the boxster would react. since it's not forced induction - i would assume it would have a far less drastic effect, but it might do something.

if it's 5-6 bucks a gallon, i'd be up for trying some. it's not THAT expensive. put in 5 gallons, then top off with the regular stuff, like 91 here in CA, and then the mixture will be 93ish. there are tables you can find online if you goggle that will tell you waht overall octane you wind up with if you mix 100 and 91 in differen concentrations.

i know the EVO/STi guys have a lot of custom maps and they actually can get computers with switches on them, ,and depending on what octane gas they are running, they flip the switch to go between the 91/93 map, and the 100map. on highly tuned cars, the difference in power thye make on a tuned 100 map is huge.

i kinda think on our cars, that while yhou may feel it, it's not going be so drastic that you become "hooked" on it like you would if you had a turbo car.

that's a good thing! i blew so much money on gas and it was drag to then drive the car on "normal" gas after having access to 100. it's a good thing to have a car that doesn't NEED high octane to run right given how much it costs and what a PITA it is to have to always need it.

let us know how you like it. i'm tempted to go buy some and try it. i moved, so I no longer have easy access to 100, but there is a gas station about 25 miles away that has it.... close enogh to "try" but not close enough to "use".
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Old 04-23-2009, 09:42 PM   #11
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Originally Posted by 23109VC
i used to own a highly modded Volvo S60R. that car LOVED 100 octane. there was a gas station near me that sold it and I would mix in 5 gallons with a tank of 91 to net around 93-95 octane. i would also fill up two 5 gallon cans and keep it in my garage - i was addicted.

i called it "cracktane".
That makes perfect sense! Your S60R's "normal" ECU program is tuned to 93 octane. (Most performance turbo cars are.) So when you were running Kalifornia's 91 octane gas, you were most likely getting just enough knock to kick you down into the ECU's "low octane" timing table. Instant power reduction. Add in the 100-octane gas, and you're back into the "normal" timing table, and you're up 30 HP. Doesn't surprise me a bit! to you!
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Old 04-23-2009, 10:45 PM   #12
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Originally Posted by conradtan
Ah... ok. Someone told me it would be bad since the engine will be running hotter than usual. Yet another person told me higher ocatne = faster car haha!

Although its not exactly the same, a friend and I tested our 4 stroke 450cc MX bikes with an infrared thermometer. The bikes ran about 12.5 to 1 compression so they were somewhat close to our cars. We read the temp at the exhaust port, and found 110 race gas to run 15 degrees cooler then the 91 pump gas.
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Old 04-24-2009, 06:45 AM   #13
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Originally Posted by Jaxonalden
High octane fuel doesn't necessarily burn hotter, it's simply more stable than lower octane fuel. That's why high compression engines (ours) and forced induction engines (turbo charged and supercharged) need high octane.
P.S. Adam, damn nice car!!
Hey thanks Jax, likewise! Back to the original question, as most people have already said, if you only have access to 91 then mixing in some higher oct gas or octane booster may have some benefit, but going past 93 is just going to drain your wallet unless you have a custom tune, forced induction, or raised the compression.
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Old 04-24-2009, 07:37 AM   #14
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Back to the original question, as most people have already said, if you only have access to 91 then mixing in some higher oct gas or octane booster may have some benefit, but going past 93 is just going to drain your wallet unless you have a custom tune, forced induction, or raised the compression.
Yes this is true. I think our ECU can compensate till 95-96 Octane.

Here'a a mixture of 91 Octane and 100 Octane to get your desired octane mixture that I received from Unocal several years ago.
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Old 04-24-2009, 02:07 PM   #15
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Well I've run my tank to about half full now and will stop by that station to fill it up with the "good stuff" for the weekend! We'll see how it goes! Hehe... Thanks for input fellas!
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Old 04-24-2009, 02:46 PM   #16
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Quote:
Originally Posted by Jaxonalden
High octane fuel doesn't necessarily burn hotter, it's simply more stable than lower octane fuel. That's why high compression engines (ours) and forced induction engines (turbo charged and supercharged) need high octane.

If you run 87 in the for mentioned engines, without a knock sensor retarding the timing, you'll damage the engine because of pre ignition.

The engine will be livin' the good life on 100, Europe has 98 everywhere and I can't tell you how well 1.1 and 1.8 liter cars run.

P.S. Adam, damn nice car!!

The motor will run smoother on 100 octane, that's all.. The DME won't compensate for it because it only compensates up to 93 octane.

Euro 98 octane is equivalent to 91-92 octane in the US because of the different rating system: AKI (Ron+Mon/2) in the US and Ron in the EU.

Also, a partial or combination fill of different octanes, such as 50% 91 octane and 50% 100 octane does absolutely nothing, contrary to a common misconception! It does not average out to 95.5 or anything else.

Each octane mix has a different chemical composition. What we call gasoline can have as many as 90 different chemicals making up the mix, even for the same brand, same octane, in different regions and even different refinery batches. It's just that this combination (whatever it may be), acts the same as a certain combination of 2,2,4-trimethylpentane and n-heptane when put in a variable compression test engine - octane. More importantly, each has a different specific gravity. They do NOT mix!

Instead, one of the fuels will be heavier and sink below the other in the tank. First you'll burn one octane until the tank drains it, then you'll burn the second octane. Unless you had an agitator in the tank, or were pulling extremely violent maneuvers (constantly) you would NOT be delivering a dose of each fuel to the cylinders at the same time.

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Old 04-24-2009, 03:08 PM   #17
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Hey Lil B what about toluene, I read once ( I think it was here) of people using it in place of booster buying it in bulk. What wasn't clear to me was where to get it without ending up on the homeland security Christmas card list.
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Old 04-24-2009, 07:01 PM   #18
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Hey Lil B what about toluene, I read once ( I think it was here) of people using it in place of booster buying it in bulk. What wasn't clear to me was where to get it without ending up on the homeland security Christmas card list.

You can get Toluene (aka methyl benzene) at Home Depot, Loews, Menards, even Sherwin Williams - by the gallon.

There are two problems with Toluene as an octane booster:

First, it's very nasty stuff to be handling and breathing, a neurotoxin by definition.

Second, at it's highest effective concentration, it will at best only raise the octane rating of premium fuel one point. Toluene is very rich in carbon and can very quickly foul your plugs. Also, because it is an excellent solvent, it readily attacks any rubber or plastic components in the fuel system - lots of those these days.

The only time Toluene was used extensively in fuel was in the old days of forced induction or turbocharged cars in formula one racing. But it was actually used to lower the octane rating of the primary fuel - Methanol.

Toluene has an octane rating of 124 (RON), while Methanol has a Ron rating of 115 octane. Perhaps counterintuitively, these could be mixed in certain combinations to produce a 100 octane mixture which was the maximum octane allowed by the FIA.

The advantage to this mix over conventional 100 octane racing fuel was that Methanol contains a significant amount of oxygen in it's chemical makeup and so acts like a natural turbocharger, allowing more oxygen into the cylinder. The FIA has since changed the rules which now specify ordinary pump gas (albeit well refined).

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Old 04-24-2009, 08:05 PM   #19
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Instead, one of the fuels will be heavier and sink below the other in the tank. First you'll burn one octane until the tank drains it, then you'll burn the second octane. Unless you had an agitator in the tank, or were pulling extremely violent maneuvers (constantly) you would NOT be delivering a dose of each fuel to the cylinders at the same time.
This cannot be true. Gas stations sell 89 octane by mixing 87 octane and 91 octane at the pump (gas stations only have 2 tanks: 1 for 91 and 1 for 87... 3 if they have diesel). They do mix.
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Old 04-24-2009, 09:17 PM   #20
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This cannot be true. Gas stations sell 89 octane by mixing 87 octane and 91 octane at the pump (gas stations only have 2 tanks: 1 for 91 and 1 for 87... 3 if they have diesel). They do mix.
Well, yes... and no.

Mid-range octane is an alternative. It is the product of not mixing the base stocks of gasoline, but rather the dilutiion of the additives present in higher octane fuel. This is usually a 65.25:1 mix of the premium with regular.

It's more of a marketing alternative than anything. I'm not aware of any car which specifies mid-grade fuel. These are usually designed for premium, but have ECUs which will 'allow' lower grades to be used. Most engine software today follows the principle of 'follow the knock sensor'. That is they run the most retarded spark they can until a knock sensor indicates a need to advance the spark. Since this is done many, many times per second, the driver rarely experiences knock.

I mentioned the need to agitate or mechanically mix the fuels. This is not done in the tank, but at the pump itself with blending valves and so mathematically, complies with the state law that the minimum octane on the pumps sticker is being pumped. But, not any batches of 87 and 91 will do. Only batches from the same refinery and manufacturer, since different brands use different proprietary formulations and chemicals such as MBTE or Ethanol as octane boosters. Not all of these will mix and in some cases will cancel each other out.

The base stocks do in fact separate with time, but with the now dilluted additives attached. If it didn't, gasoline couldn't even be refined since the refining process relies on differing specific gravities to separate the components of crude components.

If you plotted the DMEs spark adavance, you'd see one setting for 65% of the tankful and another for 35% of the tankful. The driver would be oblivious to the different settings because no knock would occur through the tankful.


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