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Old 07-23-2010, 12:34 AM   #1
Subyroo2.5
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Default Best fuel?

Does it matter where you buy fuel? Do some gas station additives run better in our cars than others?

BTW: sounds like a dumb question, but I have heard of people who sent out fuel for analysis and said that 76 and shell were the best.
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Old 07-23-2010, 01:25 AM   #2
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not really in stock trim 89 is fine but if you have a tune and advanced timing or cams or high compression..better be 93 or race gas in that thing(high compression is higher than stock like 12:1) other than that just make sure the gas station gets gas delivered regularly..not once a week or once every two weeks..the more a gas station gets there gas delivered..the more you know theres likely no rust or water in there wells...down here the gas station I go to gets gas 3 times a week..which is good..you always get gas from the middle never from the bottom or top...
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Old 07-23-2010, 01:39 AM   #3
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Originally Posted by VIsubi View Post
not really in stock trim 89 is fine but if you have a tune and advanced timing or cams or high compression..better be 93 or race gas in that thing(high compression is higher than stock like 12:1) other than that just make sure the gas station gets gas delivered regularly..not once a week or once every two weeks..the more a gas station gets there gas delivered..the more you know theres likely no rust or water in there wells...down here the gas station I go to gets gas 3 times a week..which is good..you always get gas from the middle never from the bottom or top...

Im speaking more towards the additives. I recall vishnu tuning in cali dyno testing different fuels and finding that 76 was the best???

Last edited by Subyroo2.5; 07-23-2010 at 02:13 AM.
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Old 07-23-2010, 02:04 AM   #4
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Old 07-23-2010, 09:10 AM   #5
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Sooooo.... basically, every gas station is fine.

There are some people that swear they can tell a difference when they fill up at gas station Brand A instead of Brand B. I've never noticed any difference. I stick to name brands, mostly because I trust their supply chain. I have no idea where Jim Bob's Gas and Bait gets his gas from, so I avoid it unless I absolutely can't.

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Old 07-23-2010, 12:06 PM   #6
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Quote:
Originally Posted by VIsubi View Post
...just make sure the gas station gets gas delivered regularly..not once a week or once every two weeks..the more a gas station gets there gas delivered..the more you know theres likely no rust or water in there wells...down here the gas station I go to gets gas 3 times a week..which is good..you always get gas from the middle never from the bottom or top...
There is so much stupid in this quote that I refuse to believe that this guy is serious, let alone clean of hallucinogens, ever again.
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Old 07-23-2010, 12:09 PM   #7
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Interestingly enough, my 2.5i wagon on 87 knocks or pings alot. I changed over to 93 and it doesn't happen. When I am tight on money and go back to 87, the pings/knocks start again.

The gas station or company has no affect, it's the octane for my car that makes the difference and I haven't read much about others having the same issue.

With the A/C, I have to 93 or my car cries like a baby.
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Old 07-23-2010, 12:23 PM   #8
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i pump 93 into my 2.5i. other people tell me that its stupid but its only a bit more and it can't actually hurt the car.
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Old 07-23-2010, 12:32 PM   #9
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Quote:
Originally Posted by LetItSnow View Post
There is so much stupid in this quote that I refuse to believe that this guy is serious, let alone clean of hallucinogens, ever again.
Can you be more specific? While I agree that his time metrics probably don't mean much, there is definitely something to be said for not buying old, stagnant gas. A small, independent station that doesn't see a lot of business is much more likely to have bad gas than a name brand station that is being regularly topped off with fresh fuel.

Quote:
Originally Posted by cbxp View Post
other people tell me that its stupid but its only a bit more and it can't actually hurt the car.
It also isn't doing anything to help the car. But it's only money, right?

With that said, how many of us change our oil way more frequently than we need to and/or use synthetic oil when we really don't need to? Many of us (myself included) spend money that we don't really need to spend because we think it's "better" for the car.
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Old 07-23-2010, 12:58 PM   #10
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^^ putting 93 in might be a waste of money but if you read my post #7, the 93 octane rids my car of the pining or knocking or whatever it's called.

When the engine is under load like with A/C, the 93 actually makes an even bigger difference in ridding that noise.

I wonder if something is amiss with my wagon? 35K miles, 30K done by local suby buddy who works for a suby service dept.
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Old 07-23-2010, 01:05 PM   #11
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Funny thing about various gas station "brands":
In actuality, all the gas trucks (76, Shell, Arco) fill up from the exact same refinery (locally speaking, not interstate). There was a study done a few years back that followed the gas trucks from various gas stations, and found that both the "cheap" and "expensive" gas comes from the exact same source, the local refinery. The only differences are the post-production additives (i.e. Techron, etc) that are designed to burn cleaner. So basically the need to spend "x" for "y" gas is purely marketing
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Old 07-23-2010, 01:29 PM   #12
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Quote:
Originally Posted by kero View Post
^^ putting 93 in might be a waste of money but if you read my post #7, the 93 octane rids my car of the pining or knocking or whatever it's called.

When the engine is under load like with A/C, the 93 actually makes an even bigger difference in ridding that noise.

I wonder if something is amiss with my wagon? 35K miles, 30K done by local suby buddy who works for a suby service dept.
Yes, something is wrong with your car. When I read your comment the first time I missed that your car was a newer model. If it's actually knocking and pinging then the knock sensor isn't doing its job. Normally a dead knock sensor would pretty much put the ECU in limp mode, pulling a lot of timing to keep the engine "safe", so the fact that you're not getting a CEL and not seeing horrible performance indicates that something is definitely not right.

Quote:
Originally Posted by Steckers View Post
The only differences are the post-production additives (i.e. Techron, etc) that are designed to burn cleaner. So basically the need to spend "x" for "y" gas is purely marketing
Except for the post-production additives, which I'm pretty sure is what this thread is about.
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Old 07-23-2010, 01:46 PM   #13
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A gas station that gets a fill every two weeks on an 8000 gallon tank, sapping the tank top to bottom, will average 6 ten gallon fills per hour. He's basically saying to stay away from any gas station that's completely nowhere near anything, mostly because it's probably closed because sales were so dismal.

I'm interested in hearing how you can draw gas from an underground tank from the middle - not the top, not the bottom - just because they fill three times a week. The tanks I'm familiar with (found in truly populated areas!) feed their pumps at the bottom and filter the fuel before it gets to your nozzle. It's a matter of physics supporting getting the fuel above the pavement.

How much sediment could you get in an underground tank? Think about it - it's getting diluted by thousands upon thousands of gallons of gas a week.

You'd pretty much have to be at the gas station at the end of Terminator to be concerned about trouble from the tank.
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Old 07-23-2010, 04:41 PM   #14
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Quote:
Originally Posted by kero View Post
^^ putting 93 in might be a waste of money but if you read my post #7, the 93 octane rids my car of the pining or knocking or whatever it's called.

When the engine is under load like with A/C, the 93 actually makes an even bigger difference in ridding that noise.

I wonder if something is amiss with my wagon? 35K miles, 30K done by local suby buddy who works for a suby service dept.
What does 93 octane do for your car that 89 or 91 wouldn't? There's no way your stock tune non-turbo car NEEDS 93 octane to avoid detonation, unless there is something wrong with your car.
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Old 07-23-2010, 05:45 PM   #15
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excess carbon in engine might add to the octane requirement for gas! Try autorx or MMO before next oil change and see if that helps.
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Old 07-23-2010, 05:53 PM   #16
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Quote:
Originally Posted by kero View Post
Interestingly enough, my 2.5i wagon on 87 knocks or pings alot. I changed over to 93 and it doesn't happen. When I am tight on money and go back to 87, the pings/knocks start again.

The gas station or company has no affect, it's the octane for my car that makes the difference and I haven't read much about others having the same issue.

With the A/C, I have to 93 or my car cries like a baby.
What I said earlier plus
Octane does not slow flame speed; it simply delays the initial combustion

so a lower octane fuel used does not delay initial combustion and the excess carbon in the combustion chamber might create hot spots causing pre ignition which goes away when you use the higher octane fuel. Did your buddy change the oil frequently?
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Old 07-23-2010, 06:11 PM   #17
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Originally Posted by bangedlegacywagon97 View Post
excess carbon in engine might add to the octane requirement for gas!
When I asked My local Suby Tech, 'is running higher octane ok'
He said, there is no added benefit, but, it may lead to carbon buildup.

So now I'm curious.

-I echo most the sentiments in this thread regarding sticking to 'major brand' stations that are reasonably busy. And sticking to your recommended octane rating as put forth in the operating manual.

WoO0o!!
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Old 07-23-2010, 07:09 PM   #18
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damn you guys.. im considering pumping only 87 again. but something just feels wrong about it not sure if you know what i mean.
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Old 07-23-2010, 08:27 PM   #19
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I hadn't seen anything under 87 octane until I went to the pumps with a rental in Colorado, facing the option of 85!
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Old 07-23-2010, 08:58 PM   #20
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Higher octane is better; i was referring to Arco's 87 vs Shell's 87 (i.e. same octane at different stations). Before I got tuned, I had switched to to 89 (from 87, which is the basic here in Cali). When I did that helped out my car alot.
Now after having been tuned I'm running 91 all the time (highest out here, with the except of Trick Fuel, @ $8/ gallon )
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Old 07-23-2010, 10:26 PM   #21
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Quote:
Originally Posted by Patrick Olsen View Post
Yes, something is wrong with your car. When I read your comment the first time I missed that your car was a newer model. If it's actually knocking and pinging then the knock sensor isn't doing its job. Normally a dead knock sensor would pretty much put the ECU in limp mode, pulling a lot of timing to keep the engine "safe", so the fact that you're not getting a CEL and not seeing horrible performance indicates that something is definitely not right.


Except for the post-production additives, which I'm pretty sure is what this thread is about.
Patrick, as much as it pains me to say this.....Your wrong.

The 06+ 2.5i's run like hammered dog crap on 87. They ping and thus pull timing on loads at certain RPM's. Switching to 91 this week I noticed an instant difference. This has also been logged by several people.

Also the IAM's are higher on our newer models while running higher octane.

I'm not talking about a ferrari vs honda difference but in layman's terms the car is happier on high octane
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Old 07-23-2010, 10:29 PM   #22
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Originally Posted by Steckers View Post
Funny thing about various gas station "brands":
In actuality, all the gas trucks (76, Shell, Arco) fill up from the exact same refinery (locally speaking, not interstate). There was a study done a few years back that followed the gas trucks from various gas stations, and found that both the "cheap" and "expensive" gas comes from the exact same source, the local refinery. The only differences are the post-production additives (i.e. Techron, etc) that are designed to burn cleaner. So basically the need to spend "x" for "y" gas is purely marketing

Correct. My original question applied to the additives. Maybe there is so little additives that it makes no difference, but maybe some companies use more and some use less. Maybe the additives lower the octane? I have researched this and googled that and have found no studies or lab analyisis of different brands of fuel.
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Old 07-23-2010, 10:45 PM   #23
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Originally Posted by Subyroo2.5 View Post
Patrick, as much as it pains me to say this.....Your wrong.

The 06+ 2.5i's run like hammered dog crap on 87. They ping and thus pull timing on loads at certain RPM's. Switching to 91 this week I noticed an instant difference. This has also been logged by several people.

Also the IAM's are higher on our newer models while running higher octane.

I'm not talking about a ferrari vs honda difference but in layman's terms the car is happier on high octane
This is so true. Before I got tuned for 91, I would run 87. On 87, my engine sounded like there was a damn marching band drumline in there. 89 helped out quite a bit, but there is absolutely no ping whatsoever now that I am tuned.
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Old 07-24-2010, 10:54 AM   #24
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Originally Posted by Subyroo2.5 View Post
Patrick, as much as it pains me to say this.....Your wrong.

The 06+ 2.5i's run like hammered dog crap on 87. They ping and thus pull timing on loads at certain RPM's. Switching to 91 this week I noticed an instant difference. This has also been logged by several people.

Also the IAM's are higher on our newer models while running higher octane.

I'm not talking about a ferrari vs honda difference but in layman's terms the car is happier on high octane
Wow I am so happy to know that there are others out there that noticed the same thing about the 2.5i's and 87 octane.

I knew nothing was really wrong with my car as she runs fine and smooth other than the pinging, which only happens on 87 octane.

The other interesting thing which is normal I think, is that between 87 and 93, on 93 my gas mileage is def better.

So, thanks for all the comments guys on my particular posts in this thread.
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Old 07-24-2010, 07:22 PM   #25
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on '05 to '09 RS/2.5i (probably many older and newer models also) 87, 89, 91 and 93 octane gas will still not have the anti-detonation properties to avoid timing advance from being reduced (IAM < 1 (16 on 16-bit ECU)) 93oct will allow the most timing advance to be used. for example, on a 75F day 93oct resulted in an IAM of 0.9xx. 87oct resulted in an IAM of 0.675. This data is true for my '07 with the factory EL manifold and factory exhaust with hybrid intake and stock tune. The colder the intake air temp the more timing advance can be used typically. without an IAM of 1.000 (16 on 16-bit ECU) the ECU has determined that knock has occurred in at least one load/engine speed area and it has removed timing advance to eliminate the knock. this means that there is less tq being made at that load/rpm than could be. It also makes it more likely that knock may occur at other load/rpm's. BUT, the ECU should do its job well enough to keep detonation under control for the typical daily driver. It has to knock initially for the ECU to be able to recognize that timing advance needs to be reduced, if it in fact does need to be reduced.

miliage will increase and more tq will be made anytime more timing advance can be used. So higher octane gas will result in a little bit more power and slightly better miliage.

Blame the aggressive factory tune for this. It does maximize the potential of the gas being used at the cost of an increased risk to knock.
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