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Oops - I filled up with regular (87 octane gas) - will it hurt the car


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I accidently filled up with regular unleaded (87 octane) rather than the recommeded super unleaded (91 octane). I know the computer will adjust the timing so that the engine will run on lower octane (albeit with less HP), but will the prolonged period of running a full tank of 87 hurt the engine in any way?

The 996 owner's manual says that the car will operate normally on at least 95 RON (I think 87 octane is about 91 RON?), so that doesn't sound good. Should I siphon out the gas?

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I accidently filled up with regular unleaded (87 octane) rather than the recommeded super unleaded (91 octane). I know the computer will adjust the timing so that the engine will run on lower octane (albeit with less HP), but will the prolonged period of running a full tank of 87 hurt the engine in any way?

The 996 owner's manual says that the car will operate normally on at least 95 RON (I think 87 octane is about 91 RON?), so that doesn't sound good. Should I siphon out the gas?

longhorn,

I would not siphon the gas, but would put some octane booster you can purchase from an auto supply to get the octane closer to normal dependent on how much your tank was filled with the 87 octane fuel. I would try and "take it easy" in driving for a 1/4 of a tank or so until you can get some 91 ( or higher if available in your area).

demosan

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I would do the same thing. Drive it easy till you can get a full tank of 91 in there. I

would drive it till I had it half empty and fill it up. I would then drive it till it needs a

full tank.

Paul

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I accidently filled up with regular unleaded (87 octane) rather than the recommeded super unleaded (91 octane). I know the computer will adjust the timing so that the engine will run on lower octane (albeit with less HP), but will the prolonged period of running a full tank of 87 hurt the engine in any way?

The 996 owner's manual says that the car will operate normally on at least 95 RON (I think 87 octane is about 91 RON?), so that doesn't sound good. Should I siphon out the gas?

No. It will not hurt the car.

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I accidently filled up with regular unleaded (87 octane) rather than the recommeded super unleaded (91 octane). I know the computer will adjust the timing so that the engine will run on lower octane (albeit with less HP), but will the prolonged period of running a full tank of 87 hurt the engine in any way?

The 996 owner's manual says that the car will operate normally on at least 95 RON (I think 87 octane is about 91 RON?), so that doesn't sound good. Should I siphon out the gas?

No. It will not hurt the car.

I disagree, if the computer does not have enough threshold to detune to 87, yes it could hurt the car by detonating. Just the mere fact you are over 11:1 compression ratio, I don't think the maps will accomadate 87. So throw in octane booster and when down to 1/2 tank fill it with 93 and octane and booster again.

Do not drive it hard until you can at least get 93 and octane booster in together.

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I have used 87 octane in my Boxster for 9 years. While I may not be going to Porsche heaven, I can't tell the difference between 87 and 91.

Too Pants, don't say that! You are destrying my logic for paying 14 cents a liter more for 94 octane gas everytime I go to the Chevron station! :o

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I accidently filled up with regular unleaded (87 octane) rather than the recommeded super unleaded (91 octane). I know the computer will adjust the timing so that the engine will run on lower octane (albeit with less HP), but will the prolonged period of running a full tank of 87 hurt the engine in any way?

The 996 owner's manual says that the car will operate normally on at least 95 RON (I think 87 octane is about 91 RON?), so that doesn't sound good. Should I siphon out the gas?

Accoding to what I was told at the factory when I picked up my '01 the engine ECU compares the initial detonation, detected via the newer (then) wide-band non-resonant knock/ping sensors, with crank timing to determine if any corrective action is required/needed. If the (even minor) detonation is prior to the spark ignition then the mixture will be enriched since it would make no sense to adjust the ignition timing.

I was told that in my travels I would not always be able to fuel with premium and that wouldn't be a problem but I was to absolutely avoid fueling with leaded absent encurring a fee to install new catalytic converters prior to US shipment.

Edited by wwest
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This is all speculation, anyone without seeing the maps to say the computer will detune to 87 is just making assumptions. I believe it will to 91 but since the recommended is 93, I would not make that assumption!

I know for a fact that maps that I was involved with Ford and GM, the threshold was not that robust to allow such a wide margin of error. Yes it will attempt to retard the spark, and adjust the fuel flow, but some maps are not that robust to get you that far below the recommendation.

Based on the lower limit of not allowing it to detune that far it can only offset some detonation.

BTW on some cars high speed detonation may not even be audible!

So unless someone can show the actual fuel map. I would not speculate on anything!

So why take a chance!

Edited by KevinMac
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This is all speculation, anyone without seeing the maps to say the computer will detune to 87 is just making assumptions. I believe it will to 91 but since the recommended is 93, I would not make that assumption!

I know for a fact that maps that I was involved with Ford and GM, the threshold was not that robust to allow such a wide margin of error. Yes it will attempt to retard the spark, and adjust the fuel flow, but some maps are not that robust to get you that far below the recommendation.

Based on the lower limit of not allowing it to detune that far it can only offset some detonation.

BTW on some cars high speed detonation may not even be audible!

So unless someone can show the actual fuel map. I would not speculate on anything!

So why take a chance!

It is NOT speculation. This is a fact and is easily proven by monitoring your sensors. Spend some money on a scanner and have yourself a look. As a matter of fact, if the ambient temperature is cold enough and engine temps are low, timing is often not retarded, even when running 89 octane.

Edited by 1999Porsche911
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The August 3rd NY Times had an article about this very subject. They spoke with PNA which said that any of their modern cars (which I'd interpret to be water cooled at a minimum) can be run on regular fuel without the risk of damage. The spokesman for PNA did say that if you want maximum performance you would not use 87.

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This is all speculation, anyone without seeing the maps to say the computer will detune to 87 is just making assumptions. I believe it will to 91 but since the recommended is 93, I would not make that assumption!

I know for a fact that maps that I was involved with Ford and GM, the threshold was not that robust to allow such a wide margin of error. Yes it will attempt to retard the spark, and adjust the fuel flow, but some maps are not that robust to get you that far below the recommendation.

You really don't need to take the time to tell us just how far behind the technology "curve" Ford and GM are, we're all, hopefully, very well aware of that. Even my '92 LS400, with the old style resonant knock/ping sensors, has enough range to adjust for regular fuel.

Based on the lower limit of not allowing it to detune that far it can only offset some detonation.

BTW on some cars high speed detonation may not even be audible!

So unless someone can show the actual fuel map. I would not speculate on anything!

And just how many of us out here in the peanut gallery do you think would even understand the actual fuel map....??

So why take a chance!

And wouldn't it be somewhat idiotic for Porsche to design a car that didn't have enough parametric mapping range, A/F mixture and/or timing adjustment, for use in a country/region/continent where premium fuel is often not available...??

Edited by wwest
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This is all speculation, anyone without seeing the maps to say the computer will detune to 87 is just making assumptions. I believe it will to 91 but since the recommended is 93, I would not make that assumption!

I know for a fact that maps that I was involved with Ford and GM, the threshold was not that robust to allow such a wide margin of error. Yes it will attempt to retard the spark, and adjust the fuel flow, but some maps are not that robust to get you that far below the recommendation.

You really don't need to take the time to tell us just how far behind the technology "curve" Ford and GM are, we're all, hopefully, very well aware of that. Even my '92 LS400, with the old style resonant knock/ping sensors, has enough range to adjust for regular fuel.

Based on the lower limit of not allowing it to detune that far it can only offset some detonation.

BTW on some cars high speed detonation may not even be audible!

So unless someone can show the actual fuel map. I would not speculate on anything!

And just how many of us out here in the peanut gallery do you think would even understand the actual fuel map....??

So why take a chance!

And wouldn't it be somewhat idiotic for Porsche to design a car that didn't have enough parametric mapping range, A/F mixture and/or timing adjustment, for use in a country/region/continent where premium fuel is often not available...??

Your right and premium is not available in all areas, that's why Porsche says you can run 91.

Droping 3 points is ususally not an issue, but 6 can be!

Sensors are not going to tell you anything other than they are working and depending on the one you have you will see what the outputs are. Will not tell you the combustion profile!

You have no clue by looking at a scanner and seeing if the map is at it's lowest limit unless of course it has the map download capabilities.

As I said it's all speculation!

You have to look at he actual maps! Until someone can provide the actuall map parameters, I would not stand by that 87 can be run without any damage.

But then again it's your cars do what you want!

With over 11:1 even with low ambient temps the combustion temps are higher. So lets not go that route.

Yes i have a scanner.

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This is all speculation, anyone without seeing the maps to say the computer will detune to 87 is just making assumptions. I believe it will to 91 but since the recommended is 93, I would not make that assumption!

I know for a fact that maps that I was involved with Ford and GM, the threshold was not that robust to allow such a wide margin of error. Yes it will attempt to retard the spark, and adjust the fuel flow, but some maps are not that robust to get you that far below the recommendation.

You really don't need to take the time to tell us just how far behind the technology "curve" Ford and GM are, we're all, hopefully, very well aware of that. Even my '92 LS400, with the old style resonant knock/ping sensors, has enough range to adjust for regular fuel.

Based on the lower limit of not allowing it to detune that far it can only offset some detonation.

BTW on some cars high speed detonation may not even be audible!

So unless someone can show the actual fuel map. I would not speculate on anything!

And just how many of us out here in the peanut gallery do you think would even understand the actual fuel map....??

So why take a chance!

And wouldn't it be somewhat idiotic for Porsche to design a car that didn't have enough parametric mapping range, A/F mixture and/or timing adjustment, for use in a country/region/continent where premium fuel is often not available...??

Your right and premium is not available in all areas, that's why Porsche says you can run 91.

Droping 3 points is ususally not an issue, but 6 can be!

Sensors are not going to tell you anything other than they are working and depending on the one you have you will see what the outputs are. Will not tell you the combustion profile!

You have no clue by looking at a scanner and seeing if the map is at it's lowest limit unless of course it has the map download capabilities.

As I said it's all speculation!

You have to look at he actual maps! Until someone can provide the actuall map parameters, I would not stand by that 87 can be run without any damage.

But then again it's your cars do what you want!

With over 11:1 even with low ambient temps the combustion temps are higher. So lets not go that route.

Yes i have a scanner.

And, like I said, it is NOT speculation. And, in fact. your scanner CAN tell you exactly what the maps are doing. The DME not only adds fuel to the engine with each signal from the knock sensors, but retards the timing by approximately 4 degrees each time all the way down to 8 degrees advanced under load.

It may be speculation to you, but is a fact to those who know. Low octane by itself does not always cause detonation, anyway.

Additionally, ANY early detonation WILL create noise that will be picked up by properly functioning knock sensors, whether you hear them or not.

Edited by 1999Porsche911
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I bow to the self proclaimed experts who know nothing about the mapping software and insist that the scanner watching the sensors tell the combustion profiles! No longer worth the discussion! Do what you like it's your vehicle!

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I bow to the self proclaimed experts who know nothing about the mapping software and insist that the scanner watching the sensors tell the combustion profiles! No longer worth the discussion! Do what you like it's your vehicle!

Okay, question for you, then.

With the A/F mixture and ignition timing "mapping software" so easily malable/modified and regular fuel less expensive and such a common thing why wouldn't the parametric mapping ALWAYS allow for the use of regular fuel. What's the harm...??

Wouldn't it take a somewhat idiotic engineering team, engineering management, to overlook such capability..??

Allow an engine, "street" engine, to be damaged as the result of an owners simple oversight/mistake...??

NOT..!!

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I bow to the self proclaimed experts who know nothing about the mapping software and insist that the scanner watching the sensors tell the combustion profiles! No longer worth the discussion! Do what you like it's your vehicle!

Okay, question for you, then.

With the A/F mixture and ignition timing "mapping software" so easily malable/modified and regular fuel less expensive and such a common thing why wouldn't the parametric mapping ALWAYS allow for the use of regular fuel. What's the harm...??

Wouldn't it take a somewhat idiotic engineering team, engineering management, to overlook such capability..??

Allow an engine, "street" engine, to be damaged as the result of an owners simple oversight/mistake...??

NOT..!!

No because they already specified the fuel that should be used! Porsche and other performance cars are fighting the battle between performance and emissions! To just say you can use this fuel and to design with such wide paramaters is a false understanding!

It's a myopic view to think it's as easy as your comment!

Those who buy these cars are expeced to want the performance, therefore the price of fuel is not a factor. If that is your concen then go buy a honda!

With your logic on street engine, then 87 must be okay in a non natually aspirated street engine too? Hey the guy made a mistake and put in the wrong fuel!

Go try and get a warranty claim done if it's found out the so called street engine did not use the recommended fuels!

BTW when you go get a tune, guess what, they tune to the fuel being used. So turn the question around, if you get a performance tune what makes you think you can step down from the design? It is a bad assumption on your part!

So to respond on your comment NOT! Nice try though!

Edited by KevinMac
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I bow to the self proclaimed experts who know nothing about the mapping software and insist that the scanner watching the sensors tell the combustion profiles! No longer worth the discussion! Do what you like it's your vehicle!

Okay, question for you, then.

With the A/F mixture and ignition timing "mapping software" so easily malable/modified and regular fuel less expensive and such a common thing why wouldn't the parametric mapping ALWAYS allow for the use of regular fuel. What's the harm...??

Wouldn't it take a somewhat idiotic engineering team, engineering management, to overlook such capability..??

Allow an engine, "street" engine, to be damaged as the result of an owners simple oversight/mistake...??

NOT..!!

No because they already specified the fuel that should be used! Porsche and other performance cars are fighting the battle between performance and emissions! To just say you can use this fuel and to design

with such wide paramaters is a false understanding!

Yes, all of <6% between 87 and 92 octane..!!

It's a myopic view to think it's as easy as your comment!

Those who buy these cars are expeced to want the performance,

therefore the price of fuel is not a factor.

In our travels throughout europe fuel price, while SUPER expensive even for regular, was not the issue, availability of premium was.

If that is your concen then go buy a honda!

With your logic on street engine, then 87 must be okay in a non natually aspirated street engine too?

Again, other than designed strictly for race use, yes.

Take, for example, the Mazda CX-7 turbo 4 cylinder, recommended fuel is premium, minimum fuel octane is 87. Stated right there on their home page.

Hey the guy made a mistake and put in the wrong fuel!

Go try and get a warranty claim done if it's found out the so called street engine did not use the recommended fuels!

BTW when you go get a tune, guess what, they tune to the fuel being used.

What tune, which modern day street use car requires a "tune"...??

So turn the question around, if you get a performance tune what makes you think you can step down from the design? It is a bad assumption on your part!

So to respond on your comment NOT! Nice try though!

"if you get a performance tune..."

Pardon my ignorance but I have no idea what you mean by that, with today's engines just what is, what consitutes, a "performance tune"..??

Edited by wwest
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So let me get this straight you are comparing a Mazda CX 7 a passenger crossover vehicle vs a performance car, wow! We are talking Porsche a performace vehicle!. Once again would you really put 87 octane in Carrera turbo "street engine"?

Well if you don't know what a performane tune is, which there are many avialable for Porsche, how can you comment on the acceptable fuels to use?

Oh btw if I remember correctly most European countries have a minimum or "regular"@ 95 RON which is = to 91 in the US. Kinda matches the octane recommendatin in the owners manual 91 to 93! Funny how that works out!

With that said, all I am saying is I would not make any speculation on using 87 unless Porsche says it's okay, or someone has looked at the maps! To just randomly say you can use it is nothing but speculation.

Check this out from PCA - looks like what I have been saying.

http://www.pca.org/tech/tech_qa_question.a...9-50218293CFDC}

Edited by KevinMac
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To remedy low octane, I would avoid using regular octane booster (just a few snippets from the web: http://www.automotivehelper.com/topic458390.htm).

The most effective way, albeit not cheapest, to boost your octane is xylene, available at Homedepot, Lowes or Sherwin Williams.

I buy it by the 5 gal. can for trackevents in the summer, when high temps tend to increase the engine's octane requirements.

In your case 13 gal. of 87 + 2 gal. of xylene would restore your total octane to 91. In lower concentrations (<45% total aromatics in your tank) the xylene is not supposed to have negative effects on hoses etc.

For more interesting reading see here: http://www.elektro.com/~audi/audi/toluene.html (As stated at the end of the article, toluene and xylene are very similar chemically and in their behaviour as octane boosters).

Joost

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So let me get this straight you are comparing a Mazda CX 7 a passenger crossover vehicle vs a performance car, wow! We are talking Porsche a performace vehicle!. Once again would you really put 87 octane in Carrera turbo "street engine"?

If the tank is empty, and only regular is available, yes, absolutely YES..!!

Well if you don't know what a performane tune is, which there are many avialable for Porsche, how can you comment on the acceptable fuels to use?

NO comment.

Oh btw if I remember correctly most European countries have a minimum or "regular"@ 95 RON which is = to 91 in the US. Kinda matches the octane recommendatin in the owners manual 91 to 93!

Funny how that works out!

Yes, LOL, it is funny, truly FUNNY..

"to provide optimum performance and fuel economy Porsche recommends unleaded premium fuel with an octane rating of 98 RON (93 CLC or AKI)."

"be assured that your vehicle will operate properly with octane numbers of at least 95 RON (90 CLC or AKI)....

So, by your "standards" when we in the US fuel with premium we're really using "regular" as defined by Porsche..??

Would that mean their premium is ~100 octane....??

With that said, all I am saying is I would not make any speculation on using 87 unless Porsche says it's okay, or someone has looked at the maps! To just randomly say you can use it is nothing but speculation.

Check this out from PCA - looks like what I have been saying.

http://www.pca.org/tech/tech_qa_question.a...9-50218293CFDC}

Edited by wwest
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