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  #13  
Old 09-06-2015, 09:36 PM
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Re: For those with the Hemi engine, 87 or 89 octane?

I've used 89 octane in my hemi ever since day one. It's what's recommended in the owners manual. I want all of my 360 horses performing at their maximum potential at all times

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  #14  
Old 09-07-2015, 07:33 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

Quote:
Originally Posted by peckmv View Post
I have tested both octanes and recorded the mileage from both with no difference in mileage. If there was any HP change it was unnoticeable. I did notice that the knocking stopped when I went with 89. The knocking only occurred when towing or climbing a steep hill, while using 87.
That sounds like what they had in mind with the 87 ok, but 89 recommended.

Ford recommends 87 for their 2.0 Ecoboost. But they say that the 240 stated horsepower was achieved using 93, which should be used when towing.


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Old 09-07-2015, 08:10 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

Quote:
Originally Posted by silvermax04 View Post
I think which is better depends on your situation, normal climate just running around the suburbs 87 is fine. High temp climates towing or running jeep under load id go with the 89.
This I agree with. Extremely high temperatures can cause engine knock. Here in Phoenix Summertime temperatures can easily run 115F+. I run 91 Octane Premium. Several stations here have stopped carrying "Mid Grade 89", and I'm not running 87 Octane in a HEMI in those temps. I just don't think it's smart.

Yes, the computer will automatically make adjustments to prevent severe knocking, or any damage. But in the process it will reduce power because the only way to compensate is to retard the timing. The engines are pretty much the same. The way they're controlled is different and more advanced with modern computer technology.


I paid $3,200.00+ for the HEMI. I want everything it can deliver. Otherwise what's the point? I'll save the few bucks somewhere else. I don't drive enough for it to matter. Besides, Premium is cheaper now than Regular was just a few months ago. Right now I'm averaging 18.0 MPG in my 5.7 HEMI, with power to spare. And I haven't had it in "ECO Mode" since I turned out of the dealer to bring it home.
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Old 09-07-2015, 08:17 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

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Originally Posted by bill_de View Post
That sounds like what they had in mind with the 87 ok, but 89 recommended.
That's what my manual says as well. The way I look at this, it's a bit like the FDA saying, "It's OK for consumption...... Except for women who are pregnant". Well, if it's no good for them, how the hell is it "OK" for me?

I put these fuel "recommendations" into much the same category. If 89 Octane is "recommended", then that is the bare minimum the engine should have..... Period. You can burn 87, just like pregnant women can smoke and drink.
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Old 09-07-2015, 08:28 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

Quote:
Originally Posted by bill_de View Post
Ford recommends 87 for their 2.0 Ecoboost. But they say that the 240 stated horsepower was achieved using 93, which should be used when towing.
If that statement by Ford is true, (and I believe it is), it proves that burning high Octane Premium DOES in fact increase said engines horsepower. Why would the HEMI be any different?
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Old 09-07-2015, 09:16 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

Quote:
Originally Posted by billt View Post
If that statement by Ford is true, (and I believe it is), it proves that burning high Octane Premium DOES in fact increase said engines horsepower. Why would the HEMI be any different?
It is the same for the HEMI. When you burn a lower octane fuel the timing is retarded and the vehicle is not running at its full capability. Since the timing can only be advanced so far, going to a higher octane then recommended will have no effect on power.

While the difference in power is real, the magnitude of the increase during normal driving is more in the mind than anything else. IMHO


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  #19  
Old 09-07-2015, 09:28 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

Quote:
Originally Posted by bill_de View Post
Ford recommends 87 for their 2.0 Ecoboost. But they say that the 240 stated horsepower was achieved using 93, which should be used when towing.
Quote:
Originally Posted by bill_de View Post
Since the timing can only be advanced so far, going to a higher octane then recommended will have no effect on power.
So then Ford is lying.
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Old 09-07-2015, 10:05 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

Quote:
Originally Posted by billt View Post
So then Ford is lying.
No, Ford recommends 93 octane for maximum power, so that's not a "higher octane than recommended" .. apparently the ECU can dial in enough advance to take advantage of it.
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  #21  
Old 09-07-2015, 10:26 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

I use 91 here in the mountains in the JGC and the Ram 1500 but both have Hemifever 91 tunes.


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Old 09-07-2015, 10:49 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

In my 2005 GC Hemi that I had for nearly 6 years, I ran 87 in it and was happy. But then someone on this forum really recommended 89 so once the 87 ran almost dry I filled up with 89. I DID notice a difference --- remember in 6 years of owning that GC Hemi I was well tuned to its responsiveness and power. I never went back to the 87 again. In my 2011 GC Hemi I used 89 the entire time and in my 2014 GC Hemi I have used 89 and REC 90 (90 octane without ethanol). REC 90 is quite a bit more money and only one gas station near me carries it so sticking with 89. I agree with the other posters that 89 is a more "spirited" driving experience and you bought a Hemi for a reason so why cut it short unless you are driving a ton of miles and 89 is just too costly. Good luck!
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  #23  
Old 09-07-2015, 11:13 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

Quote:
Originally Posted by tomk View Post
No, Ford recommends 93 octane for maximum power, so that's not a "higher octane than recommended"
The quote states:

Quote:
Originally Posted by bill_de View Post
Ford recommends 87 for their 2.0 Ecoboost. But they say that the 240 stated horsepower was achieved using 93, which should be used when towing.
They, (Ford) RECOMMEND 87 Octane..... Period. However, they also state if you want the maximum power the engine is capable of producing, you have to burn 93 Octane Premium. In essence they're "recommending" a lesser Octane fuel than it takes to get the rated horsepower. Why, I have no idea. Most likely to allow the most reduced operating cost. This makes the vehicle more cost competitive to operate over the long haul.

All I'm saying is why wouldn't the exact same apply to the 5.7 HEMI? Chrysler RECOMMENDS 89 Octane Mid Grade. That doesn't mean the engine will produce 360 H.P. on that fuel. It more than likely won't.

According to Ford, it requires going from the RECOMMENDED 87 Octane, all the way to 93 Octane, in order to achieve the maximum rated horsepower. That's a full 6 Octane swing. The highest possible at the pump in this country. Few stations even carry 93 Octane Premium. Around here only some Chevron stations and Shell V-Power Premium advertise 93 Octane. All the rest are 91.

So... Considering all of that, it would make sense to achieve the maximum rated horsepower of 360 in the Jeep 5.7 HEMI, you would have to burn higher than the RECOMMENDED 89 Octane in order to do it.

As far as I'm concerned, this is all a play on words, nothing more. Today's V-8 engines have variable everything. Years ago they did not. Both valve timing, and well as spark advance, were set and locked at the time of tune up. You either burned Premium, (or "Eythl" as it was called then), in high performance V-8's, or else you could induce spark knock or detonation so bad you could knock holes in your pistons.

Today with modern computer controls that is not the case. You can burn reduced Octane fuel, and the engines computer will compensate by effectively "detuning" the engine as you drive, to accept it without any harm. But, computers are not magical. If you want full power, you have to burn the highest Octane fuel to get it.
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Old 09-07-2015, 11:50 AM
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Re: For those with the Hemi engine, 87 or 89 octane?

And FCA states for the 5.7L...

"The manufacturer recommends the use of 89 octane for optimum performance. The use of premium gasoline is not recommended, as it will not provide any benefit over regular gasoline in these engines."
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