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Old 09-06-2013, 08:48 PM   #31
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XZY and TOK,

Check out the link earlier in the thread: Pentastar Engines: Overview and Technical Details

Modern engines do have the ability to automatically advance or retard timing to find the combustion sweet spot. Advancing the timing tends to do a couple things - a more efficient burn, and more heat produced. The only time this would not occur is if you were at the point of most efficient/complete combustion - there would be nothing more to gain by advancing the timing further.

What is important to remember here is that refers to IGNITION timing, not valve timing. High performance engines tend to run more valve overlap (intake and exhaust valves open at the same time). Variable valve timing was/is a big deal because a specific valve timing is best for specific combustion conditions. The two work independently. So, regardless of the fuel you run, your engine can still shift the valve timing for additional performance.

Most vehicles are designed to run the fuel specific in the manual - their combustion efficiency and valve timing are optimized for that fuel. Going to a less volatile, higher Octane fuel will not yield any significant result, or, often, any results at all because any marginal gain in efficiency from a minor timing advance is offset by the lower power production inherent to higher Octane levels.

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Old 09-06-2013, 10:00 PM   #32
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The 3.6 motor has 10.2 compression ratio. Without computer controlled timing you would destroy the motor in one trip to the grocery store using 87 octane. The computer retards timing to compensate for the octane level. If you run a higher octane then the the timing is more advanced and hence more HP. I run 93 all the time not only because of the octane, but because it is the only grade available in NC with no ethanol. I find it worth the price difference.
Absolutely incorrect. Modern engines are designed to run with a tune which is geared to a fixed point. If the engine is tuned for 87, and you filled it with 93 it will still run at an 87 level with extra heat as a byproduct. This is why you have things like the diablo chip, to retune the fuel map and take advantage of the higher octane. If you can get more power simply by filling up with better gas all the chip companies would go bankrupt tomorrow. Now, if you filled your motor with 80 octane (let's say for the sake or argument it exists) then your knock sensor would retard timing, limp your motor, and save itself from internal damage until the bad/incorrect fuel is burnt off or extracted. You filling up with 93 is nothing more than butt dyno wishes. Your pissing your money away.

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Old 09-06-2013, 10:01 PM   #33
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If he is running a cold air intake, I can see where you get more dust but if it is just a replacement filter for the original and the box is closed, I don't see how it could get any more dust than the original.
More airflow means it is restricting (filtering) less air than a stock filter. Thus, more dirt particles can get through. That's OK for racing applications where an engine gets rebuilt often. Not so much for a passenger vehicle.

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Old 09-06-2013, 10:05 PM   #34
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Let the oil companies rob you as little as they can.

I spend 2 grand a week on fuel though
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Old 09-06-2013, 10:14 PM   #35
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More airflow means it is restricting (filtering) less air than a stock filter. Thus, more dirt particles can get through. That's OK for racing applications where an engine gets rebuilt often. Not so much for a passenger vehicle.

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Thats not totally true either. Filters dont filter by restricting air flow.

Funny thing, ive been involved in racing. Knew guys who didnt run filters at all running in martin michigan right after they rebuilt the place. No grass whatsoever cause they started using the facility too quick after seeding.

Guys had dirt caked in intake manifold.......still ran fine.

We ran k&n, our engines were clean......
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Old 09-06-2013, 10:38 PM   #36
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Use regular. Using Premium or higher octane fuel is worthless and maybe harmful. The higher the octane rating the higher the fuel's resistance to burning.
Some funny staff ^ Resistance to the DETONATION, burning is what is always inside of your and everyone's engine. Detonation is similar to explosion, while such engine could be damaged. So, higher octane can't damage anything. It possibly does some small difference to the mpg, but not very significant while we all driving box shaped cars like Wrangler.
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Old 09-06-2013, 10:41 PM   #37
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Unfortunately, the general public is highly susceptable to marketing. Gas companies will occasionally promote using higher grades for better performance. The problem is that they don't elaborate that you'll get that better performance IF YOUR CAR IS ENGINEERED TO RUN ON THE HIGHER OCTANE. So, yeah, just read the manual. If you have a Porsche 911, yeah, you need the 91-93 octane. Got a Jeep Wrangler? Just use 87.
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Old 09-06-2013, 11:16 PM   #38
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Unfortunately, the general public is highly susceptable to marketing.
Highly susceptible...period.

If regular gas was actually 87 octane like advertised, you would all have a point. However, I find it unlikely that we're getting the octane printed on that pump.

Inaccurate octane rating is a common violation at gas stations. I wouldn't be surprised if that 87 is often an 85, and those "fools" buying the 89 are the ones getting the 87 octane fuel that's recommended for this motor.
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Old 09-07-2013, 12:17 AM   #39
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Most manufacturers don't recommend high octane for compressions any lower than 10:1, and to my knowledge, JKs run at 9.6:1... so it's higher than an average car that might be 8:1, but it is still under the bare minimum and the owner's manual recommends 87. If running 89 makes you feel better, it's highly unlikely it will hurt the engine. 91 is both unnecessary and can cause issues, 91 is not "better" or "cleaner", and can cause issues if the compression isn't high enough for it, mainly with your valves and seals leaking oil.

And I whole heartedly agree with those that said if you get knocking with 87, either the gas is very dirty, and/or you have other problems- higher octane isn't the solution.

I used to own a bmw 540i, and the dealership mechanics told me to only ever buy from Shell or Chevron, because they maintain their tanks better, and I would get knock if I filled up at Circle K, or several other places with cheaper prices. Also, never fill up during or immediately after the station is being refilled by a tanker. All the sediment in the station tanks is being stirred up and you will get cruddy gas. If you see a place being filled, it's best to wait a few hours, or just go someplace else.

Hope some of that helped.
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Old 09-07-2013, 12:26 AM   #40
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Highly susceptible...period.

If regular gas was actually 87 octane like advertised, you would all have a point. However, I find it unlikely that we're getting the octane printed on that pump.

Inaccurate octane rating is a common violation at gas stations. I wouldn't be surprised if that 87 is often an 85, and those "fools" buying the 89 are the ones getting the 87 octane fuel that's recommended for this motor.
This is based on what scientific testing and repeatedly conducted where? Gas stations aren't lowering the octane, the refiners would have to be the ones doing it

If your theories are true, we better all go down to the airport and start paying $5.58 per gallon or more for 100 octane LL avgas.
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Old 09-07-2013, 12:31 AM   #41
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Every few weeks this comes up on this forum. I work in an oil refinery. As far as using anything in your Jeep other than what the owner's manual calls for, that's foolish. I will let you in on some secrets. Most of the nation's refineries are on the coasts. Gas stations close to those refineries get their gas at the refineries. Stations that don't have their own refinery nearby buy it from one that is local. If you move inland, the trucks pick up from terminals where we all ship gasoline to them via pipeline and it all gets mixed together in the tanks. The only thing you are getting different from another station is the additive. There isn't a requirement for how much additive, either. It can be one drop per tanker. Also be aware that just because it says one name on the sign, it's not necessarily that station. I work for an independant refiner, meaning we don't drill. We own hundreds of Shell stations in the Bay Area. Not one of them is actually Shell and if you look at the very fine print you will see it says, "operated by xxxxxx". You might also notice that none of the fuels say Shell with V-Power-their additive. To make it even more confusing, at my refinery, we have a Chevron terminal where their trucks come in and pick up fuel to take to their stations. On top of that, we all buy fuel from each other during maintenance shutdowns to fulfill our contracts. Ultimately, buy the cheapest gas at the recommended octane and if you want Techron, go buy it in the bottle at the auto parts store. It will still be cheaper.
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Old 09-07-2013, 06:00 AM   #42
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Every few weeks this comes up on this forum. I work in an oil refinery. As far as using anything in your Jeep other than what the owner's manual calls for, that's foolish. I will let you in on some secrets. Most of the nation's refineries are on the coasts. Gas stations close to those refineries get their gas at the refineries. Stations that don't have their own refinery nearby buy it from one that is local. If you move inland, the trucks pick up from terminals where we all ship gasoline to them via pipeline and it all gets mixed together in the tanks. The only thing you are getting different from another station is the additive. There isn't a requirement for how much additive, either. It can be one drop per tanker. Also be aware that just because it says one name on the sign, it's not necessarily that station. I work for an independant refiner, meaning we don't drill. We own hundreds of Shell stations in the Bay Area. Not one of them is actually Shell and if you look at the very fine print you will see it says, "operated by xxxxxx". You might also notice that none of the fuels say Shell with V-Power-their additive. To make it even more confusing, at my refinery, we have a Chevron terminal where their trucks come in and pick up fuel to take to their stations. On top of that, we all buy fuel from each other during maintenance shutdowns to fulfill our contracts. Ultimately, buy the cheapest gas at the recommended octane and if you want Techron, go buy it in the bottle at the auto parts store. It will still be cheaper.
Very interesting. I knew some of this but didnt realize they might only use a drop of additivr in a tanker. I drive a food grade tanker and honestly their could be a drop of bird crap in there and it wouldnt affect the product!

I always laugh at people that just have to go to the same gas station, even at the expense of running out...lmfao.

I run a cetane booster in the truck when its going to be below 20 and i plan on shutting the truck off. Cetane being the opposite of octane.....a measure of how easily fuel preignites. Hell most people dont even know diesel freezes.
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Old 09-07-2013, 08:02 AM   #43
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MD,

Oh, anyone that's been stationed in Alaska, Fort Drum, Germany or Korea can tell you diesel freezes - or, as is often the case with JP-8, turns to a not very tasty slushy. You are not alone in feeling that pain.

The thing about compression in engines - it's been going up across the board and will continue to do so until available technology and production makes it impractical. Higher compression = higher efficiency - so, there is an incredibly strong motive for engineers and auto makers to get on that band wagon. Combustion efficiency doesn't just mean better fuel economy, it also means more power.

Higher compression does not always mean higher Octane required, either. As a case in point, Suzuki designed the older generations of the GSX-R to run 87 Octane pump gas with compression ratios of 12:1 or greater. A big player in this is how effectively your engine cools itself. Whether you use more timing advance or more compression, better cooling means a lower overall temperature and prevents detonation. Better cooling, on its own, also increases theoretical efficiency and engine performance.
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Old 09-07-2013, 08:10 AM   #44
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Lookup http://www.toptiergas.com/retailers.html

Its what I've been using/getting 87 gas from and ive noticed an improvement on my 08 jku. Lot less hesitation when accelerating and mpg seems to be alittle bit better
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Old 09-07-2013, 08:17 AM   #45
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page 513 owners manual.
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Old 09-07-2013, 09:38 AM   #46
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The 3.6 motor has 10.2 compression ratio. Without computer controlled timing you would destroy the motor in one trip to the grocery store using 87 octane. The computer retards timing to compensate for the octane level. If you run a higher octane then the the timing is more advanced and hence more HP. I run 93 all the time not only because of the octane, but because it is the only grade available in NC with no ethanol. I find it worth the price difference.
This poster ALMOST hit the nail on the head. I am a professional drag racer over the last 8 yrs. and he is completely correct about 10.2 compression ratio needing high octane fuel, without retarding the timing the engine definitely would be toast. The only item in question is 93 octane gas having no ethanol content, ethanol is the component in gasoline that ENHANCES the octane level for the fuel since they have outlawed the other chemical additives. The Computer cannot sense octane level of your fuel, therefore it will not advance your timing giving you more horsepower. Flex fuel vehicle can sense the ethanol content in the fuel adjusting the timing to compensate ADDING timing for the HIGHER percentage of ethanol. I run E-98 in a supercharged engine with a compression ratio of 19 to 1. Ethanol is a great performance fuel if the engine is made to accept it.
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Old 09-07-2013, 01:18 PM   #47
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Lookup Top Tier Gasoline

Its what I've been using/getting 87 gas from and ive noticed an improvement on my 08 jku. Lot less hesitation when accelerating and mpg seems to be alittle bit better
Top TIER certified fuel is also what I try to stay with. The owner's manual in at least one of my Chrysler vehicles says to use it and I've had good results. No reason to switch.
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Old 09-07-2013, 05:58 PM   #48
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I have been building race motors for 40 years. 87 octane is s***!
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Old 09-07-2013, 06:02 PM   #49
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I have been building race motors for 40 years. 87 octane is s***!
A race motor compared to the motor in a Jeep is apples to oranges.
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Old 09-07-2013, 06:17 PM   #50
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i would recommend staying away from Ugas stations and racetrac... their prices are usually cheaper but i feel its a lesser quality of fuel. speaking of gas with 10% ethanol, i don't think nowadays you can find gas without it.... at least here in florida thats for sure.
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Old 09-07-2013, 07:07 PM   #51
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IF you "think our 89 is actually 87" then you need to contact your state office of weights and measures and file a complaint, because they are the ones who test and certify that the fuel at the pump meets the standards.

But here is a little secret....there is no such thing as mid-grade (89 octane) gasoline. Mid-grade is actually mixed at the pump; it's just a blend of regular unleaded and high octane unleaded...seriously. No 18 whee tanker is hauling around mid-grade; they only produce 2 grades of fuel for the retail automotive consumer.
While the trend is moving towards blend dispensers many stations still prefer non-blenders. My company has installed non-blender s at 10 stations in the last year. These stations have Mid-grade blended at the bulk plant and delivered by 18 wheelers.
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Old 09-07-2013, 11:53 PM   #52
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This is based on what scientific testing and repeatedly conducted where? Gas stations aren't lowering the octane, the refiners would have to be the ones doing it

If your theories are true, we better all go down to the airport and start paying $5.58 per gallon or more for 100 octane LL avgas.
If you do a quick search you'll see that during sporadic testing by XYZ agencies there are always violations found, one of which is octane mislabeling. I'm not saying it happens at the majority of pumps, but it definitely still happens, most likely with 87 gas being passed off as plus or premium as the most common example. We all know that shady things happen at gas stations, and we know that no one cares about your car or your engine except you. Unless you test the gas you're buying, you don't know what you're getting either
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Old 09-08-2013, 05:54 AM   #53
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Go ahead and run leaded gas. Youll plug your catalytic converter up..........air planes have straight pipes.....guess you could run one of those too.

We have a few stations that sell torco 110 octane locally. Maybe the 100ll is being mislabeled and its just 87 octane!!
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Old 09-08-2013, 12:41 PM   #54
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Octane

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I have been building race motors for 40 years. 87 octane is s***!
Over octane levels are just as bad as under octane due to the fuel burn characteristics (speed) If the manual says 87 octane that's what I would burn.
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Old 09-08-2013, 05:54 PM   #55
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page 513 owners manual.
You probably believe Obama when he says Obamacare will save you money!
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Old 09-08-2013, 06:26 PM   #56
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Some years back when I was a forced induction enthusiast I decided to learn about fuels.

Long story short, the info I got by corresponding and talking with the engineers at some of the major oil companies is that burn speed is NOT a function of octane level. One engineer told me that one of their high octane race fuels had the fastest burn speed of any fuel they made.

Now don't ask me to document this. I went through all this years ago. For years I kept the names, dates, titles, company info and quotes of what they told or wrote me.... Because it was contrary to what is commonly held as fact on the Internet forums. I have no interest in putting out all that effort again or arguing with strangers on the web. If you don't want to believe it, fine by me. Perhaps the engineers were wrong. Just thought you might find that info curious, as I did.
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Old 09-08-2013, 06:27 PM   #57
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The Wranglers compression ratio is simply not that high - this will come off as rude, but it seems that one does not need to know engines all that well to drive one to its limits. Sort of a Days of Thunder type scenario.

This thread is a classic example of why doing your own research and making your own decision is a far better choice that watching the digital spectacle.
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Old 09-08-2013, 06:38 PM   #58
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PS - I find my 2013 does not detonate on 87 octane, and that is what matters. If you found your rig dets under load, say maybe during very hot dry weather like you might find going up grades in the summer in the desert, there is nothing wrong IMO with using 89. Detonation is one of the worst possible things for your engine.

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