wifey says fill it up with 87
01-18-2011, 08:39 PM
#51
Re: wifey says fill it up with 87
I'm still with 1move on this. I know this thread will not really help anyone here. If it is highly recommended to use 91 Octane, so be it.
If the OP is referring to me as one of those people posing as a technical speciallist. I am not. Bottom line is, if I were to buy a car between one being fuelled with 91 Octane vs 87 Octane. I know, without a doubt I will choose a car fuelled with 91 Octane (yes, many can argue as well that people can advertise that it was always fuelled with 91 Octane, even if it wasnt). I was always taught a golden rule "Do onto others, as you would like others do onto you".
The way I viewed the wifes comment of not caring of who will use it next kind of bothered me. Also, what if using a lower ocatane showed considerate amount of engine problem. They find out it was due to not following the recommendations. You are liable for it. On the other hand, if the engine showed damages, yet you tell them you religously followed the recommendations, at least you have something to argue with.
If the OP is referring to me as one of those people posing as a technical speciallist. I am not. Bottom line is, if I were to buy a car between one being fuelled with 91 Octane vs 87 Octane. I know, without a doubt I will choose a car fuelled with 91 Octane (yes, many can argue as well that people can advertise that it was always fuelled with 91 Octane, even if it wasnt). I was always taught a golden rule "Do onto others, as you would like others do onto you".
The way I viewed the wifes comment of not caring of who will use it next kind of bothered me. Also, what if using a lower ocatane showed considerate amount of engine problem. They find out it was due to not following the recommendations. You are liable for it. On the other hand, if the engine showed damages, yet you tell them you religously followed the recommendations, at least you have something to argue with.
01-18-2011, 08:43 PM
#52
Audi Forum - Posts like an A5
Join Date: Oct 2010
Location: Republic of B.C.!
Posts: 382
Re: wifey says fill it up with 87
If you really need to pay the extra change for the upgrade to premium or super duper grade gasoline. The answer to that question is no. Unless you're driving one of the very small percentages of performance vehicles with an engine designed specifically to utilize the properties of higher-octane premium gasoline, there is no performance gain in using premium. It might make you feel better, but your engine won't know the difference.
For the most part, vehicles made after 1985 or so should run just fine on regular 87-octane gasoline. The good majority of engines out on the road today have relatively low compression ratios, and are well suited to use with regular gasoline. There are of course exceptions to every rule: if you're out on the street running a high-compression engine in a racecar disguised as a grocery getter, then you know who you are and know what you need. Understanding what octane is and why there are different grades of gasoline begins with a simplified version of engine operation and straight chain hydrocarbons.
Knock, Ping and Detonate
In a four-stroke engine, the pistons are doing one of four things: taking in a breath of fuel and air into the cylinder through the intake valve, compressing the air and fuel mixture for a spark induced burn, turning the energy created by that burn into a downward power stroke, or expelling that same burnt up mixture out an open exhaust valve on the upstroke. When a piston travels up in the cylinder it reaches the point called top dead center. At this point the piston can travel up no more and, by virtue of being connected to an ever-spinning crankshaft via a connecting rod, must travel back down the cylinder again. For peak efficiency the compressed fuel should start to burn only an instant after the piston reaches top dead center on the compression stroke and the spark lights the mixture.
Even more importantly the fuel-air mixture must burn in an even flame front originating from the spark created by the spark plug. If the fuel-air mixture ignites on its own before it is sparked, this out-of-time explosion produces an audible knock that makes your engine suddenly sound like a clothes dryer full of rocks. What's happening is that an explosion is occurring out of time and ahead of the burning mixture created by the spark. Instead of one even burn propelling the piston back down the cylinder to make power, two out-of-time-explosions are competing against each other. The sound this competition creates is known as knocking, pinging, or detonation and is unfortunately the sound of engine damage!
Detonation is extremely tough on pistons, valves, connecting rods, bearings, and cylinder walls. If your vehicle is not one of the high performance few, but knocks away anyway when you hit the gas after pouring the 87 octane in the tank, then there are more nefarious causes at work under your hood.
Hexane, Heptane, Octane, Flame
From the sludge that is crude oil, straight chain hydrocarbons are refined and lined up in a row to put the tiger in your tank. The greater number of molecules in the chain, the more resistant to compression-induced ignition the fuel is. Octane has eight molecules in the chain like an Octopus has eight legs. The real difference between 87-octane regular gasoline and 91-octane premium is the rate at which it burns when compressed and ignited while inside your engine.
The compression ratio of a given engine is what determines its octane requirements. Since most engines have a compression ratio designed for 87-octane unleaded fuel, all should be well in staying regular with regular. Even if you have a super-performance sportster with a big "91 ONLY" sticker on the gas cap, no harm will likely come if 87 is added by mistake. Modern engines come equipped with a knock sensing system, which listens for detonation and tells the engine computer to adjust spark timing until detonation is eliminated.
Conversely, the engine computer in a vehicle built to run on regular will not sense an increase in octane and adjust ignition timing to take advantage of the higher octane, so pouring in the premium in an engine not designed to take advantage of it is the equivalent of shooting money out of the tailpipe. All this is, of course, is a massive oversimplification, yet the fact of the matter is this: If your engine is designed to use 87 octane, yet rattles away like Carmen Miranda shaking her maracas every time you hit the gas pedal, then something is wrong and it's only going to get worse.
Less Space, More Problems
High mileage engines often suffer from a buildup of carbon deposits in the combustion chamber. This buildup causes the total volume of the combustion chamber to become smaller. This decrease in chamber volume effectively raises the compression ratio of the engine, and causes low octane gasoline to detonate, and your engine to knock. If a high-mileage engine designed for regular gas knocks unless premium is used, then carbon buildup may be the culprit.
Other causes of detonation include overheating, a malfunctioning EGR valve, too far advanced ignition timing, or a defective knock sensor. Overheating caused by a defective thermostat or cooling system negates the engine's ability to channel away heat from the combustion chamber and causes the compressed fuel to detonate. If the timing is advanced too far, the spark ignites the compressed mixture too early on the power stoke, causing detonation. A defective knock sensor can send the ignition timing pell-mell, and direct sparks into the cylinders astray.
A defective EGR, or exhaust gas recirculation valve, can also wreck havoc on fuel mixture temperature. Always follow manufacturer's recommendations for gasoline but, if your regular old gas engine knocks while drinking its regular old gas, first try switching gas stations, then consider making repairs or adjustments. You could end up saving money in the long run.
For the most part, vehicles made after 1985 or so should run just fine on regular 87-octane gasoline. The good majority of engines out on the road today have relatively low compression ratios, and are well suited to use with regular gasoline. There are of course exceptions to every rule: if you're out on the street running a high-compression engine in a racecar disguised as a grocery getter, then you know who you are and know what you need. Understanding what octane is and why there are different grades of gasoline begins with a simplified version of engine operation and straight chain hydrocarbons.
Knock, Ping and Detonate
In a four-stroke engine, the pistons are doing one of four things: taking in a breath of fuel and air into the cylinder through the intake valve, compressing the air and fuel mixture for a spark induced burn, turning the energy created by that burn into a downward power stroke, or expelling that same burnt up mixture out an open exhaust valve on the upstroke. When a piston travels up in the cylinder it reaches the point called top dead center. At this point the piston can travel up no more and, by virtue of being connected to an ever-spinning crankshaft via a connecting rod, must travel back down the cylinder again. For peak efficiency the compressed fuel should start to burn only an instant after the piston reaches top dead center on the compression stroke and the spark lights the mixture.
Even more importantly the fuel-air mixture must burn in an even flame front originating from the spark created by the spark plug. If the fuel-air mixture ignites on its own before it is sparked, this out-of-time explosion produces an audible knock that makes your engine suddenly sound like a clothes dryer full of rocks. What's happening is that an explosion is occurring out of time and ahead of the burning mixture created by the spark. Instead of one even burn propelling the piston back down the cylinder to make power, two out-of-time-explosions are competing against each other. The sound this competition creates is known as knocking, pinging, or detonation and is unfortunately the sound of engine damage!
Detonation is extremely tough on pistons, valves, connecting rods, bearings, and cylinder walls. If your vehicle is not one of the high performance few, but knocks away anyway when you hit the gas after pouring the 87 octane in the tank, then there are more nefarious causes at work under your hood.
Hexane, Heptane, Octane, Flame
From the sludge that is crude oil, straight chain hydrocarbons are refined and lined up in a row to put the tiger in your tank. The greater number of molecules in the chain, the more resistant to compression-induced ignition the fuel is. Octane has eight molecules in the chain like an Octopus has eight legs. The real difference between 87-octane regular gasoline and 91-octane premium is the rate at which it burns when compressed and ignited while inside your engine.
The compression ratio of a given engine is what determines its octane requirements. Since most engines have a compression ratio designed for 87-octane unleaded fuel, all should be well in staying regular with regular. Even if you have a super-performance sportster with a big "91 ONLY" sticker on the gas cap, no harm will likely come if 87 is added by mistake. Modern engines come equipped with a knock sensing system, which listens for detonation and tells the engine computer to adjust spark timing until detonation is eliminated.
Conversely, the engine computer in a vehicle built to run on regular will not sense an increase in octane and adjust ignition timing to take advantage of the higher octane, so pouring in the premium in an engine not designed to take advantage of it is the equivalent of shooting money out of the tailpipe. All this is, of course, is a massive oversimplification, yet the fact of the matter is this: If your engine is designed to use 87 octane, yet rattles away like Carmen Miranda shaking her maracas every time you hit the gas pedal, then something is wrong and it's only going to get worse.
Less Space, More Problems
High mileage engines often suffer from a buildup of carbon deposits in the combustion chamber. This buildup causes the total volume of the combustion chamber to become smaller. This decrease in chamber volume effectively raises the compression ratio of the engine, and causes low octane gasoline to detonate, and your engine to knock. If a high-mileage engine designed for regular gas knocks unless premium is used, then carbon buildup may be the culprit.
Other causes of detonation include overheating, a malfunctioning EGR valve, too far advanced ignition timing, or a defective knock sensor. Overheating caused by a defective thermostat or cooling system negates the engine's ability to channel away heat from the combustion chamber and causes the compressed fuel to detonate. If the timing is advanced too far, the spark ignites the compressed mixture too early on the power stoke, causing detonation. A defective knock sensor can send the ignition timing pell-mell, and direct sparks into the cylinders astray.
A defective EGR, or exhaust gas recirculation valve, can also wreck havoc on fuel mixture temperature. Always follow manufacturer's recommendations for gasoline but, if your regular old gas engine knocks while drinking its regular old gas, first try switching gas stations, then consider making repairs or adjustments. You could end up saving money in the long run.
01-18-2011, 08:58 PM
#53
Audi Forum - Posts like an A4
Join Date: May 2009
Location: Canada
Posts: 193
Re: wifey says fill it up with 87
No, it is not highly recommended. The translation is this: if you want to take advantage of all our ingenuity and efforts to created a really fine machine we recommend you using 91 and up gasoline. If you don't care about performance you are going to be just fine using 87 gas. [But, we all here at Ingolstadt f@$k you big time for that. 
]
In case she knew what the manual says, GOOD FOR HER !!! It's her choice. The car will be OK. I am pretty sure they had a conversation about this issue.
The manual says black on white that the car can be operated using 87 gas, so nobody is gonna be liable. Yes, you are liable if using leaded gasoline.
]
The way I viewed the wifes comment of not caring of who will use it next kind of bothered me.
Also, what if using a lower ocatane showed considerate amount of engine problem. They find out it was due to not following the recommendations. You are liable for it. On the other hand, if the engine showed damages, yet you tell them you religously followed the recommendations, at least you have something to argue with.
01-18-2011, 09:17 PM
#54
Re: wifey says fill it up with 87
Impolite or not Im not here to start a war, I do have a right to my opinion as do you, read the statement below and tell me how you feel about what I said about the OP then...
01-18-2011, 09:18 PM
#55
Audi Forum - Posts like a Q7
Join Date: Nov 2008
Location: Regina, SK
Posts: 725
Re: wifey says fill it up with 87
Even if you have a super-performance sportster with a big "91 ONLY" sticker on the gas cap, no harm will likely come if 87 is added by mistake. Modern engines come equipped with a knock sensing system, which listens for detonation and tells the engine computer to adjust spark timing until detonation is eliminated.
I know what I'm talking about here guys - you can easily confirm it with some good research. Bad research is randomly Googling stuff; good research is using trusted sources that are as close as possible to primary data, e.g., SAE, Engineering, and scientific, papers or websites. There are even many good forums populated mostly by Engineers or Automotive technologists that provide excellent resources. Bottom line: take the time to properly learn what you're talking about, or reference a trusted resource.
Why take such a large gamble for very little ROI?
01-18-2011, 09:30 PM
#56
Audi Forum - Posts like an A3
Join Date: Sep 2010
Location: Pemberton, BC
Posts: 84
Re: wifey says fill it up with 87
I don't disagree with you on the cost/ROI comment and use 91 in the A4. As I've said before, I've used 87 in the Volvo for 12 years and close to 300k with absolutely no problems, so will continue. I'm just interested in seeing some facts/figures on detonation disasters in daily drivers.
Cheers
01-18-2011, 09:50 PM
#58
Audi Forum - Posts like an A4
Join Date: May 2009
Location: Canada
Posts: 193
Re: wifey says fill it up with 87
Indeed, the gas cap says Premium 91 min, but at the same time shows a book, which I believe makes reference to the owner's manual. Anyway, despite the fact I am pouring 91 gas in my Audi, I do believe that the engine will not be damaged if using 87. I am talking strictly about an Audi A4, and not about high performance cars with '91min Only' on the sticker. [For these cars the link posted by Mona said that the engine will not be damaged if 87 gas is accidentally used.]
And when it comes to what OP said about not being his moral responsibility, as long as the manual says that 87 gas can be used, he is absolutely right. I have no doubts. It would have been a totally different story if he ignored something stated in the manual saying: constant usage of 87 gas instead of 91 min will damage the engine. I am pretty sure that the Audi's law department knows very well how to keep somebody liable for an improper use of its cars.
Last edited by maxaudi; 01-18-2011 at 10:01 PM.
01-19-2011, 07:58 AM
#59
Audi Forum - Posts like an HORCH
Join Date: Dec 2009
Location: Burlington, Ontario
Posts: 2,719
Re: wifey says fill it up with 87
Evidence of damage caused by pre-detonation using wrong grade of fuel
http://www.mlcmotorfactors.co.uk/Tro...s/GasketTT.pdf
http://www.mlcmotorfactors.co.uk/Tro...s/GasketTT.pdf
01-19-2011, 08:50 AM
#60
Audi Forum - Posts like an A4
Join Date: May 2009
Location: Canada
Posts: 193
Re: wifey says fill it up with 87
I have no doubts that one of the causes for abnormal combustion (pre-ignition and irregular detonation) is the use of a lower grade gas, but the document is very-very general.
I will try to define my position again, maybe better:
1. Is the 91 and up gas recommended by Audi (engineers, and mechanics) ? Yes.
2. Is the 91 and up gas going to produce a slightly (according to the manual) better performance of the Audis ? Yes.
3. Is it better worth the difference in funds to use 91 gas ? Yes.
4. Do I agree with the previous statements, and fill up my tank with 91 gas ? Yes.
5. Do the engineers and mechanics from Audi tell me that using 87 gas is okay, but make me aware that I will have a slightly lower performance because of that ? Yes. It is stated in my car's manual. And again: there is no addendum to that statement.
6. Do the engineers and mechanics from Audi tell me that using 87 gas continuously will damage the engine of my car ? NO (!!!) If anybody knows differently please show us the documentation .
Now, for 1Move and Cheeba:
1Move: If you are trying to convince us that using 91 and up gas in our Audis is much better, then I totally agree with you. If this is the case I must apologize for not getting your idea. But if you are trying to convince us that using 87 will damage the engine... well, you have to prove that, because according to the manual you are wrong. It will be absolutely beneficiary for everybody here if you can prove that - documentation, or anything else -, but without any prove that's called speculation.
Cheeba: do you know of one case at least when an Audi engine was damaged - proven and documented - because the owner used 87 gas instead of 91 ?
Guys please do not take it personally; it's not my intention to launch a personal attack, but I trust more the engineers and mechanics from Audi then you guys. That's all.
I will try to define my position again, maybe better:
1. Is the 91 and up gas recommended by Audi (engineers, and mechanics) ? Yes.
2. Is the 91 and up gas going to produce a slightly (according to the manual) better performance of the Audis ? Yes.
3. Is it better worth the difference in funds to use 91 gas ? Yes.
4. Do I agree with the previous statements, and fill up my tank with 91 gas ? Yes.
5. Do the engineers and mechanics from Audi tell me that using 87 gas is okay, but make me aware that I will have a slightly lower performance because of that ? Yes. It is stated in my car's manual. And again: there is no addendum to that statement.
6. Do the engineers and mechanics from Audi tell me that using 87 gas continuously will damage the engine of my car ? NO (!!!) If anybody knows differently please show us the documentation .
Now, for 1Move and Cheeba:
1Move: If you are trying to convince us that using 91 and up gas in our Audis is much better, then I totally agree with you. If this is the case I must apologize for not getting your idea. But if you are trying to convince us that using 87 will damage the engine... well, you have to prove that, because according to the manual you are wrong. It will be absolutely beneficiary for everybody here if you can prove that - documentation, or anything else -, but without any prove that's called speculation.
Cheeba: do you know of one case at least when an Audi engine was damaged - proven and documented - because the owner used 87 gas instead of 91 ?
Guys please do not take it personally; it's not my intention to launch a personal attack, but I trust more the engineers and mechanics from Audi then you guys. That's all.
Last edited by maxaudi; 01-19-2011 at 09:03 AM.
