87 vs 91 octane
04-25-2011 | 03:04 PM
#21
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From: Arlington, TX
^^^ Agreed
04-27-2011 | 05:05 AM
#22
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Posts: 8
No.
The owners manual is referring to what is known as "Research Octane Number" or RON. It is a different method of measuring the octane of fuel. There is also a "Motor Octane Number" or MON. At the pumps in the US and Canada, octanes are measured in AKI (Anti-Knock Index). Some countries use RON to rate gasoline so the manual states the equivalent rating.
87 AKI = 91 RON
http://en.wikipedia.org/wiki/Octane_rating
07-15-2011 | 08:27 PM
#23
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From: Seattle, WA
Objective data (i.e., scientifically valid testing) would be much more helpful. I wish I could do that for us but I lack both the equipment and experience.
07-20-2011 | 01:37 AM
#24
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I have been eye balling this post but dident want to comment untill I tryed it out for myself. Best Average gas milage I ever got with a tank of 87=26.4 with 91= 27.1. I used 2 tanks of each, alternating to get a good feel before I posted. I do about 38 miles per day on the highway, and about 11 miles on city streets per day. My car is a manual, and does not know what 4K rpm's feels like yet (waiting till after I change the oil) and the only engine mod I have is a drop in K&N. More important to me than gas milage is the diffrence in throttle response. On 87, at about 2100-2900, it feels very sluggish, especially in 2nd gear. I have to wait for it to get to 3k to get any sort of power. On 91, I dont ever feel this. I have power to spare at any rpm. It could just be me, but thats how I feel about it. Do I like paying 30 cents more per gallon? Absolutly not, but like someone eles had pointed out, its less than a $5 diffrence per fill up. One less can of skoal, and I have payed for my premium gas for the week! Now all I have to do if figure out how to cut back on my nicotine addiction...........
07-20-2011 | 05:10 AM
#25
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I have a TC2 now but before all I had were Hondas wich have high compression
Hondas DOHC VTEC engines are all over 10 compression or even higher
and says 91 only or higher okey whats point the rule of thumb always has been if your compression is 10 and higher like the TC2 which uses the AR engine which is 10.4:1 use 91 now the car has 14.5 gallon fuel tank I live la so 91 about $4.50 and 87 about $4.30 87 is $62.35 and 91 is $65.25 to fill up the tank difference $2.9 you could come come up with excuses but cant afford $3 extra a tank a energy drinks cost the same old TC1 guys could argue this because of their compression 2az-fe 9.6:1 its up to you here some facts
The compression ratio of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity. It is a fundamental specification for many common combustion engines.
In a piston engine it is the ratio between the volume of the cylinder and combustion chamber when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke.[1]
Picture a cylinder and its combustion chamber with the piston at the bottom of its stroke containing 1000 cc of air (900 cc in the cylinder plus 100 cc in the combustion chamber). When the piston has moved up to the top of its stroke inside the cylinder, and the remaining volume inside the head or combustion chamber has been reduced to 100 cc, then the compression ratio would be proportionally described as 1000:100, or with fractional reduction, a 10:1 compression ratio.
A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency.[citation needed] High ratios place the available oxygen and fuel molecules into a reduced space along with the adiabatic heat of compression–causing better mixing and evaporation of the fuel droplets.[citation needed] Thus they allow increased power at the moment of ignition and the extraction of more useful work from that power by expanding the hot gas to a greater degree.[citation needed]
Higher compression ratios will however make gasoline engines subject to engine knocking if lower octane-rated fuel is used, also known as detonation. This can reduce efficiency or damage the engine if knock sensors are not present to retard the timing. However, knock sensors have been a requirement of the OBD-II specification used in 1996 model year vehicles and newer.
In other words use higher octane to reduce Knock and better A/F Ratios unless you want to be Cheap Cheap Cheap
Hondas DOHC VTEC engines are all over 10 compression or even higher
and says 91 only or higher okey whats point the rule of thumb always has been if your compression is 10 and higher like the TC2 which uses the AR engine which is 10.4:1 use 91 now the car has 14.5 gallon fuel tank I live la so 91 about $4.50 and 87 about $4.30 87 is $62.35 and 91 is $65.25 to fill up the tank difference $2.9 you could come come up with excuses but cant afford $3 extra a tank a energy drinks cost the same old TC1 guys could argue this because of their compression 2az-fe 9.6:1 its up to you here some facts
The compression ratio of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity. It is a fundamental specification for many common combustion engines.
In a piston engine it is the ratio between the volume of the cylinder and combustion chamber when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke.[1]
Picture a cylinder and its combustion chamber with the piston at the bottom of its stroke containing 1000 cc of air (900 cc in the cylinder plus 100 cc in the combustion chamber). When the piston has moved up to the top of its stroke inside the cylinder, and the remaining volume inside the head or combustion chamber has been reduced to 100 cc, then the compression ratio would be proportionally described as 1000:100, or with fractional reduction, a 10:1 compression ratio.
A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency.[citation needed] High ratios place the available oxygen and fuel molecules into a reduced space along with the adiabatic heat of compression–causing better mixing and evaporation of the fuel droplets.[citation needed] Thus they allow increased power at the moment of ignition and the extraction of more useful work from that power by expanding the hot gas to a greater degree.[citation needed]
Higher compression ratios will however make gasoline engines subject to engine knocking if lower octane-rated fuel is used, also known as detonation. This can reduce efficiency or damage the engine if knock sensors are not present to retard the timing. However, knock sensors have been a requirement of the OBD-II specification used in 1996 model year vehicles and newer.
In other words use higher octane to reduce Knock and better A/F Ratios unless you want to be Cheap Cheap Cheap
07-20-2011 | 07:28 AM
#26
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I've been using 93 and now using 91 feels sluggish 
07-21-2011 | 11:56 AM
#27
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Did you know that a well maintained vehicle can improve fuel efficiency by up to 40 per cent? Test your fuel knowledge to discover some useful tips to prolong the life of your engine and save a few dollars at the pump.
True or false?
1. All gasolines are the same.
2. Regular engine maintenance can help save you money on fuel.
3. Octane levels in fuel don't make a difference.
4. Tire pressure can affect the fuel-efficiency of your vehicle.
5. The faster you drive, the faster you burn fuel.
Answers:
1. False. "Gasoline choice plays a vital role in the cleanliness and performance of an engine," confirms Ken Mitchell, an engineer from Shell Canada.
"If you've been using a lower-quality gasoline, there may be build-up of "engine gunk," which can negatively affect engine performance. Protecting your engine from gunk is as simple as using a high-quality gasoline, like all three grades of Shell Nitrogen Enriched Gasoline."
2. True. Regular servicing and following the service recommendations for your vehicle, such as changing the air filter, spark plugs, engine oil and other fluids ensure optimum performance and fuel efficiency.
A poorly maintained vehicle can boost fuel consumption by up to 15 per cent and increases emissions by even more.
3. False. When a lower octane fuel is used in an engine designed for higher octane, engine knocking may occur, causing the car to shudder and lose performance.
Using the right octane for your engine ensures maximum fuel economy and fewer emissions.
4. True. Operating a vehicle with just one tire under-inflated by eight psi (56 kPa) can increase vehicle fuel consumption by four per cent.
5. True. The faster you drive, the more wind resistance you'll encounter and the more fuel your vehicle will consume to maintain speed.
Reducing your speed to 90 km/h from 110 km/h saves up to 20 per cent of your fuel.
www.newscanada.com
True or false?
1. All gasolines are the same.
2. Regular engine maintenance can help save you money on fuel.
3. Octane levels in fuel don't make a difference.
4. Tire pressure can affect the fuel-efficiency of your vehicle.
5. The faster you drive, the faster you burn fuel.
Answers:
1. False. "Gasoline choice plays a vital role in the cleanliness and performance of an engine," confirms Ken Mitchell, an engineer from Shell Canada.
"If you've been using a lower-quality gasoline, there may be build-up of "engine gunk," which can negatively affect engine performance. Protecting your engine from gunk is as simple as using a high-quality gasoline, like all three grades of Shell Nitrogen Enriched Gasoline."
2. True. Regular servicing and following the service recommendations for your vehicle, such as changing the air filter, spark plugs, engine oil and other fluids ensure optimum performance and fuel efficiency.
A poorly maintained vehicle can boost fuel consumption by up to 15 per cent and increases emissions by even more.
3. False. When a lower octane fuel is used in an engine designed for higher octane, engine knocking may occur, causing the car to shudder and lose performance.
Using the right octane for your engine ensures maximum fuel economy and fewer emissions.
4. True. Operating a vehicle with just one tire under-inflated by eight psi (56 kPa) can increase vehicle fuel consumption by four per cent.
5. True. The faster you drive, the more wind resistance you'll encounter and the more fuel your vehicle will consume to maintain speed.
Reducing your speed to 90 km/h from 110 km/h saves up to 20 per cent of your fuel.
www.newscanada.com
07-21-2011 | 12:17 PM
#28
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2010 Volkswagen GTI: The Effect Of Octane On Its Power
By Jason Kavanagh | April 26, 2011
A few weeks back, one of our editors filled our longterm 2010 Volkswagen GTI's tank with 87 octane. Whether VW intended for this to happen or not, reality has a way of rendering such things moot.
Then we had a bright -- if obvious -- idea: let's do a dyno test to quantify just how much power this little hatch loses as a result of the lower octane.
It went down like this: We ran that tank of 87-ish octane down to nearly empty and refilled with 87 to ensure that the only thing in the tank was 87 octane. That, and it would give the electronic German brain on board adequate opportunity to recalibrate itself for the lower octane.
Then we dynoed it, performing as many runs as necessary to achieve a stable and consistent result.
Afterwards, we ran that tank down and refilled with 91 octane (that's the highest we get for premium fuel here in California), ran that tank down and refilled again with 91. Same logic as before.
We hit the dyno rollers again a few days later. Here's the result:
Peak Power (hp) Peak Torque (lb-ft)
91 octane 207 219
87 octane 203 216
Peak numbers don't tell the whole story, as the largest observed differences at any given engine speed were 10 hp and 11 lb-ft.
In summary, 87 octane hasn't had a tremendous effect on our GTI's ability to hustle. Surprised? I was. I expected a larger difference than this.
It's likely that although the output is similar, exhaust gas temperatures may not be, as less ignition timing can be run with 87 octane. As a result, there might be:
Note that modern engine controllers are quite adept at monitoring knock activity and adjusting accordingly. I heard not a single ping when running the snot out of this car on the dyno in either test. If you put 87 octane in your twenty year-old turbo car and gave it the wood, you might make engine soup.
Speaking of dynos, we dyno-tested our GTI on 91 octane last year, so why re-test it? I wanted to ensure similar weather conditions between the two octane dyno tests to eliminate that as a variable to the extent that I could. There are certain things that are still beyond my control, and weather is one of them. Across these two dyno test days, the temperature was within 9 degrees and ambient pressure was within 0.04 in Hg. That's about as close as anyone could ask for.
Weather has a different effect on modern turbocharged cars than it does on supercharged or normally aspirated cars. Here's why: power depends largely on the airflow rate into the engine. Turbo cars have the unique ability to regulate that airflow independently of ambient air density -- unlike non-turbo engines, turbo'd ones can actively manipulate boost pressure so that the same amount of flow enters the engine over a very broad range of ambient conditions. There are limits to this, of course, but the upshot is that turbo engines don't suffer nearly the power loss of a non-turbo engine when, say, climbing a long grade.
Temperature, however, does affect how much timing a turbo engine can run (due to knock), so in that respect weather has an indirect affect on the output of a turbo engine. The thing is, weather correction factors only account for density changes, which is why SAE does not apply weather correction to turbocharged cars, and neither do we.
By Jason Kavanagh | April 26, 2011
A few weeks back, one of our editors filled our longterm 2010 Volkswagen GTI's tank with 87 octane. Whether VW intended for this to happen or not, reality has a way of rendering such things moot.
Then we had a bright -- if obvious -- idea: let's do a dyno test to quantify just how much power this little hatch loses as a result of the lower octane.
It went down like this: We ran that tank of 87-ish octane down to nearly empty and refilled with 87 to ensure that the only thing in the tank was 87 octane. That, and it would give the electronic German brain on board adequate opportunity to recalibrate itself for the lower octane.
Then we dynoed it, performing as many runs as necessary to achieve a stable and consistent result.
Afterwards, we ran that tank down and refilled with 91 octane (that's the highest we get for premium fuel here in California), ran that tank down and refilled again with 91. Same logic as before.
We hit the dyno rollers again a few days later. Here's the result:
Peak Power (hp) Peak Torque (lb-ft)
91 octane 207 219
87 octane 203 216
Peak numbers don't tell the whole story, as the largest observed differences at any given engine speed were 10 hp and 11 lb-ft.
In summary, 87 octane hasn't had a tremendous effect on our GTI's ability to hustle. Surprised? I was. I expected a larger difference than this.
It's likely that although the output is similar, exhaust gas temperatures may not be, as less ignition timing can be run with 87 octane. As a result, there might be:
- more enrichment on 87 octane, degrading full- or near-full-load fuel economy
- less altitude margin with 87 octane, and a greater power difference might be observed at high elevation. Sorry, I don't plan on repeating this test in Denver.
Note that modern engine controllers are quite adept at monitoring knock activity and adjusting accordingly. I heard not a single ping when running the snot out of this car on the dyno in either test. If you put 87 octane in your twenty year-old turbo car and gave it the wood, you might make engine soup.
Speaking of dynos, we dyno-tested our GTI on 91 octane last year, so why re-test it? I wanted to ensure similar weather conditions between the two octane dyno tests to eliminate that as a variable to the extent that I could. There are certain things that are still beyond my control, and weather is one of them. Across these two dyno test days, the temperature was within 9 degrees and ambient pressure was within 0.04 in Hg. That's about as close as anyone could ask for.
Weather has a different effect on modern turbocharged cars than it does on supercharged or normally aspirated cars. Here's why: power depends largely on the airflow rate into the engine. Turbo cars have the unique ability to regulate that airflow independently of ambient air density -- unlike non-turbo engines, turbo'd ones can actively manipulate boost pressure so that the same amount of flow enters the engine over a very broad range of ambient conditions. There are limits to this, of course, but the upshot is that turbo engines don't suffer nearly the power loss of a non-turbo engine when, say, climbing a long grade.
Temperature, however, does affect how much timing a turbo engine can run (due to knock), so in that respect weather has an indirect affect on the output of a turbo engine. The thing is, weather correction factors only account for density changes, which is why SAE does not apply weather correction to turbocharged cars, and neither do we.
07-21-2011 | 12:38 PM
#30
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Since no one has done a true test on a 2011 scion TC for 91 vs 87 or even 93 octane ratings I can go only conclude from other car tests car engine specs as a comparison
2010 Jetta 2.5l
2011 Scion TC
2010 GTi
2010 Jetta 2.5l
- Engine: 2.5L in-line 5 double overhead cam ( 9.5 :1 compression ratio ; four valves per cylinder)
- Fuel: unleaded ( 87 octane)
- Fuel consumption: city= 23 (mpg); highway= 30 (mpg); combined= 25 (mpg); vehicle range: 364 miles
- Multi-point injection fuel system
- 14.5 gallon fuel tank
- Power: 170 HP ( 127 kW) @ 5,700 rpm; 177 ft lb of torque ( 240 Nm) @ 4,250 rpm
2011 Scion TC
- Engine: 2.5L in-linefour-cylinder DOHC with variable valve timing and four valves per cylinder
- Unleaded fuel
- Fuel economy: EPA (0
:, 23MPG city, 31 MPG highway, 26 MPG combined and 378 mi. range - Multi-point fuel injection
- 14.5gallon fuel tank
- Power (SAE): 180 hp @ 6,000 rpm; 173 ft lb of torque @ 4,100 rpm
2010 GTi
- Turbo compressor
- Engine: 2.0L in-line 4 double overhead cam with VVT ( 9.6 :1 compression ratio ; four valves per cylinder)
- Fuel: premium unleaded ( 91 octane)
- Fuel consumption: city= 21 (mpg); highway= 31 (mpg); combined= 25 (mpg); vehicle range: 364 miles
- Gasoline direct injection fuel system
- 14.5 gallon fuel tank
- Power: 200 HP ( 149 kW) @ 5,100 rpm; 207 ft lb of torque ( 281 Nm) @ 1,800 rpm
07-21-2011 | 02:47 PM
#32
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Joined: Apr 2008
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From: Rockland County NY
on this forum we have had many a discussion on this subject with poor results.
http://www.yarisworld.com/forums/sho...ghlight=OCTANE
http://www.yarisworld.com/forums/sho...ghlight=OCTANE
07-21-2011 | 03:19 PM
#33
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Joined: Jun 2011
Posts: 173
From: Rochester, NY
2010 Volkswagen GTI: The Effect Of Octane On Its Power
By Jason Kavanagh | April 26, 2011
A few weeks back, one of our editors filled our longterm 2010 Volkswagen GTI's tank with 87 octane. Whether VW intended for this to happen or not, reality has a way of rendering such things moot.
Then we had a bright -- if obvious -- idea: let's do a dyno test to quantify just how much power this little hatch loses as a result of the lower octane.
It went down like this: We ran that tank of 87-ish octane down to nearly empty and refilled with 87 to ensure that the only thing in the tank was 87 octane. That, and it would give the electronic German brain on board adequate opportunity to recalibrate itself for the lower octane.
Then we dynoed it, performing as many runs as necessary to achieve a stable and consistent result.
Afterwards, we ran that tank down and refilled with 91 octane (that's the highest we get for premium fuel here in California), ran that tank down and refilled again with 91. Same logic as before.
We hit the dyno rollers again a few days later. Here's the result:
Peak Power (hp) Peak Torque (lb-ft)
91 octane 207 219
87 octane 203 216
Peak numbers don't tell the whole story, as the largest observed differences at any given engine speed were 10 hp and 11 lb-ft.
In summary, 87 octane hasn't had a tremendous effect on our GTI's ability to hustle. Surprised? I was. I expected a larger difference than this.
It's likely that although the output is similar, exhaust gas temperatures may not be, as less ignition timing can be run with 87 octane. As a result, there might be:
Note that modern engine controllers are quite adept at monitoring knock activity and adjusting accordingly. I heard not a single ping when running the snot out of this car on the dyno in either test. If you put 87 octane in your twenty year-old turbo car and gave it the wood, you might make engine soup.
Speaking of dynos, we dyno-tested our GTI on 91 octane last year, so why re-test it? I wanted to ensure similar weather conditions between the two octane dyno tests to eliminate that as a variable to the extent that I could. There are certain things that are still beyond my control, and weather is one of them. Across these two dyno test days, the temperature was within 9 degrees and ambient pressure was within 0.04 in Hg. That's about as close as anyone could ask for.
Weather has a different effect on modern turbocharged cars than it does on supercharged or normally aspirated cars. Here's why: power depends largely on the airflow rate into the engine. Turbo cars have the unique ability to regulate that airflow independently of ambient air density -- unlike non-turbo engines, turbo'd ones can actively manipulate boost pressure so that the same amount of flow enters the engine over a very broad range of ambient conditions. There are limits to this, of course, but the upshot is that turbo engines don't suffer nearly the power loss of a non-turbo engine when, say, climbing a long grade.
Temperature, however, does affect how much timing a turbo engine can run (due to knock), so in that respect weather has an indirect affect on the output of a turbo engine. The thing is, weather correction factors only account for density changes, which is why SAE does not apply weather correction to turbocharged cars, and neither do we.
By Jason Kavanagh | April 26, 2011
A few weeks back, one of our editors filled our longterm 2010 Volkswagen GTI's tank with 87 octane. Whether VW intended for this to happen or not, reality has a way of rendering such things moot.
Then we had a bright -- if obvious -- idea: let's do a dyno test to quantify just how much power this little hatch loses as a result of the lower octane.
It went down like this: We ran that tank of 87-ish octane down to nearly empty and refilled with 87 to ensure that the only thing in the tank was 87 octane. That, and it would give the electronic German brain on board adequate opportunity to recalibrate itself for the lower octane.
Then we dynoed it, performing as many runs as necessary to achieve a stable and consistent result.
Afterwards, we ran that tank down and refilled with 91 octane (that's the highest we get for premium fuel here in California), ran that tank down and refilled again with 91. Same logic as before.
We hit the dyno rollers again a few days later. Here's the result:
Peak Power (hp) Peak Torque (lb-ft)
91 octane 207 219
87 octane 203 216
Peak numbers don't tell the whole story, as the largest observed differences at any given engine speed were 10 hp and 11 lb-ft.
In summary, 87 octane hasn't had a tremendous effect on our GTI's ability to hustle. Surprised? I was. I expected a larger difference than this.
It's likely that although the output is similar, exhaust gas temperatures may not be, as less ignition timing can be run with 87 octane. As a result, there might be:
- more enrichment on 87 octane, degrading full- or near-full-load fuel economy
- less altitude margin with 87 octane, and a greater power difference might be observed at high elevation. Sorry, I don't plan on repeating this test in Denver.
Note that modern engine controllers are quite adept at monitoring knock activity and adjusting accordingly. I heard not a single ping when running the snot out of this car on the dyno in either test. If you put 87 octane in your twenty year-old turbo car and gave it the wood, you might make engine soup.
Speaking of dynos, we dyno-tested our GTI on 91 octane last year, so why re-test it? I wanted to ensure similar weather conditions between the two octane dyno tests to eliminate that as a variable to the extent that I could. There are certain things that are still beyond my control, and weather is one of them. Across these two dyno test days, the temperature was within 9 degrees and ambient pressure was within 0.04 in Hg. That's about as close as anyone could ask for.
Weather has a different effect on modern turbocharged cars than it does on supercharged or normally aspirated cars. Here's why: power depends largely on the airflow rate into the engine. Turbo cars have the unique ability to regulate that airflow independently of ambient air density -- unlike non-turbo engines, turbo'd ones can actively manipulate boost pressure so that the same amount of flow enters the engine over a very broad range of ambient conditions. There are limits to this, of course, but the upshot is that turbo engines don't suffer nearly the power loss of a non-turbo engine when, say, climbing a long grade.
Temperature, however, does affect how much timing a turbo engine can run (due to knock), so in that respect weather has an indirect affect on the output of a turbo engine. The thing is, weather correction factors only account for density changes, which is why SAE does not apply weather correction to turbocharged cars, and neither do we.
07-22-2011 | 11:16 AM
#34
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N/A vs Turbo. Unless your tC has forced induction, then it's pretty much useless. See http://www.youtube.com/watch?v=dDHwC...eature=related
British petrol's minimum rating is 95 Octane by American standard, which is the highest-available, here. In essence, whenever you buy British regular, you're buying American Premium. The higher octane rating at minimum, is around the performance area for most mid-range cars. Adding even more Octane will have less notable effect than using American low-octane as the control against British high-octane.
This test is not for the American market
07-22-2011 | 02:59 PM
#36
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07-27-2011 | 04:18 PM
#37
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From: SATX
07-27-2011 | 06:13 PM
#39
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From: Rochester, NY