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  #13  
Old 03-21-2014, 09:16 AM
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Re: Summit - V8 Hemi - Fuel choice

Running the recommended 89 octane should yield "slightly" better mpg's, but nowhere near enough to make up the usual 20 cents extra cost over regular.
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Old 03-21-2014, 10:53 AM
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Re: Summit - V8 Hemi - Fuel choice

Around here it's usually a 10 cent difference. Break-even on mid grade gas would be about .5 or .6 mpg at that point.

I guess pre-detonation ping has not been a problem for users of regular octane gas in the 5.7?
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Old 03-21-2014, 11:43 AM
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Re: Summit - V8 Hemi - Fuel choice

Quote:
Originally Posted by Rexlion View Post
Around here it's usually a 10 cent difference. Break-even on mid grade gas would be about .5 or .6 mpg at that point.

I guess pre-detonation ping has not been a problem for users of regular octane gas in the 5.7?
Any modern engine today will self adjust the timing.

Only effect from 89 to 87 should be maybe .5 MPG difference and a couple horses.

Most cars that require 89 with 87 in them you'd be hard pressed to notice the difference.

I agree with the comments about trying to access behavior during break in. Could be the transmission adapting. I believe there is a TSB out as well on V8 transmissions.

I put regular in everything regardless of what is "recommended" and no issues with cars going over 200K and fantastic MPG.

I have not heard a car ping/knock since a model year 85 or so.
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  #16  
Old 03-21-2014, 11:53 AM
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Re: Summit - V8 Hemi - Fuel choice

Anybody have actual statistics on loss of MPG using 87, or is everybody using the SWAG method?


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  #17  
Old 03-21-2014, 01:28 PM
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Re: Summit - V8 Hemi - Fuel choice

idk about the swag method..

anyways I have always run Shell 93 octane. she seems to love it.
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Old 03-21-2014, 02:06 PM
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Re: Summit - V8 Hemi - Fuel choice

I've never put 89 in my JGC...it's been run on 87 from the get-go for 30K+ miles. I've had no issues and I get very acceptable mileage...about 16.5 mpg in general rural driving (a little less in the winter as to be expected) and 20-24 mpg highway on longer excursions and depending on the terrain. But I'm also not a heavy-foot driver, having learned to eek out a little bit more while driving my previous ride, Highlander Hybrid Limited.
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  #19  
Old 03-21-2014, 02:32 PM
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Re: Summit - V8 Hemi - Fuel choice

Quote:
Originally Posted by Rexlion View Post
Around here it's usually a 10 cent difference. Break-even on mid grade gas would be about .5 or .6 mpg at that point.

I guess pre-detonation ping has not been a problem for users of regular octane gas in the 5.7?
No, it doesn't ping. More correctly, if it does the control computer catches it long before you would notice it.

You could likely run the thing for hundreds of K miles and not hurt a thing, and without a stopwatch probably wouldn't notice any differences in performance as it dials back just a teeny amount.

... I still use midgrade, only 10c difference.
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Old 03-21-2014, 02:37 PM
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Re: Summit - V8 Hemi - Fuel choice

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Originally Posted by Evolv0 View Post
idk about the swag method..

anyways I have always run Shell 93 octane. she seems to love it.
Doesn't really need it, but I tend to put at least half a tank of Shell premium in every couple thousand miles. Don't see any difference in behavior from Conoco/Phillips, Texaco, Chevron, etc. midgrade. Haven't tried the nitrogen enriched.
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Old 03-25-2014, 11:18 AM
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Re: Summit - V8 Hemi - Fuel choice

I been switching back and forth with 87 and 89 and have been noting what I put in with every fill up on fuelly.

What I have found is in the winter (we have different blends in SE Wisconsin by season), there is negligible MPG difference, so I run 87. Also, with the cold, there less risk of pinging anyway.

in the summer, I have noted a slight, maybe 1 mpg improvement using mid grade. This could be the engine adjusting for the octane or just that our summer blend gas has a ton of ethanol in it and I think the higher grades may actually have less, or at least they smell more like regular gas.

Regardless, in the summer we tow the camper a lot so I'd be using 89 for the better pinging protection anyway.

FWIW
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Old 03-25-2014, 01:28 PM
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Re: Summit - V8 Hemi - Fuel choice

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Originally Posted by Keirik View Post
Manual says 89 octane. Anything higher is a waste. Not 87, not 91, not 93, just 89 lol.
Yes, unless you have a DiabloSport.
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Old 03-29-2014, 02:09 PM
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Re: Summit - V8 Hemi - Fuel choice

Quote:
Originally Posted by Rexlion View Post
Reviving this older thread to see if anyone in the last few months has done any experimenting between regular and midgrade in their 5.7 hemi, to see if any differences in mpg or performance can be quantified. Any new data to add?
Glad you brought it back

I read on Edmunds.com that the 5.7 HEMI required 89 in my early research of the GC which wasnít an issue, but when I went to look at a GC Summit the salesman told me no.. no 87 is recommended, so thatís what the dealer put in my first tank. I have filled it twice since then and the odometer is 1,117 its setting on ľ tank I think Iíll start using the recommended 89 octane on this next fill-up and look at the mileage after 3 tanks of the 89, not that it really matters the Jeep Ownerís manual recommends it thatís what Iíll use.
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Old 03-29-2014, 02:20 PM
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Re: Summit - V8 Hemi - Fuel choice

QUOTE=rjgnwdc;1000207]Glad you brought it back

I read on Edmunds.com that the 5.7 HEMI required 89 in my early research of the GC which wasn’t an issue, but when I went to look at a GC Summit the salesman told me no.. no 87 is recommended, so that’s what the dealer put in my first tank. I have filled it twice since then and the odometer is 1,117 its setting on ľ tank I think I’ll start using the recommended 89 octane on this next fill-up and look at the mileage after 3 tanks of the 89, not that it really matters the Jeep Owner’s manual recommends it that’s what I’ll use.[/QUOTE]

It amazes me how uniformed some salesmen can be. 89 is recommended, but not required, and since 87 is cheaper, the dealers will fill them with 87 since it's OK and cheaper to do so.
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