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  #1  
Old 04-04-2011, 06:39 PM
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87 or 89 octane

I will be filling my tank for the first time with the hemi tomorrow. I know they recommend 89 in the Hemi, but I was thinking do you think you are buying old stale gas with 89 because nobody buys it or not. It was just a thought I had.
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Old 04-04-2011, 06:50 PM
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Re: 87 or 89 octane

I cant really answer your question. I have often pondered that question, I fill 89 octane in my 86 XJ(runs better with 89) I also use 89 in my Lawn Mower(s) and all my outdoor equipment as recommended Briggs and Straton in small engines.

Every time I fill up with 89 I always wonder if Im the only one who uses it!!!

I see people use 93 and 87 but never 89!!!! I tend to take notice of what people use to fill up there cars. If it were me with the Hemi I would use 87 and see how she runs. If it runs Tight with no Hesitation just stick with 87.

I see SOOOOO Many Soccer Moms with 5.7L WK's WK2 and Durangos I CAN ALMOST BET MY HOUSE that none of them has read the manual and all use 87 with NO issues.

Your Jeep Your Choice!!! But I would try 87
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Old 04-04-2011, 06:53 PM
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Re: 87 or 89 octane

A lot of us use 89 as recommended and don't have any problems whatsoever. You can use 87 but not sure of long term affects. I know the computer will adjust the timing or anything else to adjust. I have used 87 on the highway when I know I was going to burn the whole tank and didn't notice any change. This debate has occurred many times on here and most just use 89 as recommended and I haven't seen anyone complain of any problems.
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Old 04-04-2011, 08:12 PM
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Re: 87 or 89 octane

A lot, if not most, gasoline stations have only two grades (regular unleaded and premium unleaded) in their tanks. Mid-grade is blended at the pump at the time of purchase. Octane mixing is linear, half 87 octane and half 91 octane will create 89 octane. One of our local stations gives the buyer a choice of five grades 87 thru 91 octanes, all blended at the pump.
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Old 04-04-2011, 08:50 PM
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Re: 87 or 89 octane

I've not seen any gas station that doesn't blend mid-grade at the pump in quite some time.

I still find it amusing that people buy the Hemi and gush about how they want the power, then buy lower grade fuel that will result in less of that power. If the extra money for the grade of fuel will break you, what about the fuel mileage and extra initial cost? Methinks you bought the wrong vehicle if you wait until you fuel it up to start cheaping out.
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Old 04-04-2011, 08:56 PM
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Re: 87 or 89 octane

Quote:
Originally Posted by rich mac View Post
A lot, if not most, gasoline stations have only two grades (regular unleaded and premium unleaded) in their tanks. Mid-grade is blended at the pump at the time of purchase. Octane mixing is linear, half 87 octane and half 91 octane will create 89 octane. One of our local stations gives the buyer a choice of five grades 87 thru 91 octanes, all blended at the pump.
+1
I use 87 octane....manual says it's fine.
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Old 04-04-2011, 09:16 PM
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Re: 87 or 89 octane

I used 87 in my 2005 Jeep GC V8 Hemi for nearly 6 years without an issue....BUT about two moths ago I filled up with 89 on almost an empty tank and soon after a definitely noticed a difference...more peppy and more powerful. I was left thinking I should have been using 89 the whole time instead. In my 2011 Jeep GC I am and will only use 89...
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Old 04-04-2011, 09:17 PM
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Re: 87 or 89 octane

Here is another food for thought. Ive read with the hemi engine that with the dirty intake from so much blow by of the PCV valve, and if you think your actually getting 89 your not. The dirty intake is actually lowering your fuel octane level so in theroy if your putting in mid grade your actually getting regular. I installed a catch can to fix this problem. cleaning the intake when i get a chance in the next week or two and hoping the gas millage will go up a little or a little more power will come back. Back to subject. I only buy my gas from the same Shell gass station adn gas has a shelf life of 4 months before it breaks down so i know that ill empty that tank of theirs because the hemi is always hungry!!
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Old 04-04-2011, 09:32 PM
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Re: 87 or 89 octane

From what I know the octane number has to do with knock resistance. Back in the good old days, when you used the wrong grade, it let you know and you changed. These days the computer can adjust the ignition to prevent knocking.
If I had an engine that required 89 and for whatever the reason I wanted to use 87, I would test both grades for mileage and performance on the same or very similar trips over similar terrain, load and speed. If I saw no difference in power and performance I might use the 87 otherwise, 89. The reason is that I would suspect that the computer might be adjusting and hiding the true engine performance.
What I don't compromise as long as I have a choice is the use of pure gas, no ethanol blends for me.
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Old 04-04-2011, 09:36 PM
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Re: 87 or 89 octane

Isn't 89 octane = 10% ethanol which they call super unleaded? It is where I live. I only use 87 octane in my 4.7 L V8 WK. When I had a 98 ZJ 6 cylinder I used 89 octane and had to replace the fuel filter/fuel pump. 87 octane is also 10 - 15 cents more expensive here than 89 octane. In Nebraska.
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Old 04-05-2011, 08:53 AM
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Re: 87 or 89 octane

I tested 87 vs. 89 octane in my Hemi Overland, using a tankful of each on my daily commute over several weeks, and I get about 1 to 1.5 mpg better gas mileage with the 89 octane and my butt dyno tells me that I get more power as well. I posted my calculations in another thread about this, and the 1 to 1.5 mpg difference actually works out to the 89 octane actually costing a couple of dollars less per tankful because of the extra mileage.
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Old 04-05-2011, 08:59 AM
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Re: 87 or 89 octane

Quote:
Originally Posted by Technosavant View Post
I've not seen any gas station that doesn't blend mid-grade at the pump in quite some time.

I still find it amusing that people buy the Hemi and gush about how they want the power, then buy lower grade fuel that will result in less of that power. If the extra money for the grade of fuel will break you, what about the fuel mileage and extra initial cost? Methinks you bought the wrong vehicle if you wait until you fuel it up to start cheaping out.
I don't see anyone in this thread being "cheap" because of gas choice. I see a question about how not many other vehicles use 89 octane gas therefore it sits longer in the tank at the gas station (which we have answered that is is mixed at the pump so that is not a concern) and could possibly be stale.

It seems you have some jealousy over the Hemi. You seem to be in every thread like this trying to justify the v6 decision you made.
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