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Discussion Starter · #1 · (Edited)
hi all..

regarding my 2014 Jeep Summit..

After I ran through my first tank of dealer provided gas - I filled up with regular. Immediately I noticed a performance issue - not only was the car a bit sluggish - the MPG average (after reset on fill up) was way lower -- and was lower while driving.

Like to get your opinion on fuel for the hemi based on your experience. What are you guys putting in and what is your experience...

Subsequently - I ran the tank to half and put in premium - effectively having a full take of a mid range octane... The car ran much better (still not as good as when I picked it up with dealer gas)... Maybe the gas I got at second fill up was sub parr - it was from Sams club - Ive never had problems there.

Thanks! Appreciate your advice. I know what the manual says - looking for your opinions and experience...
 

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hi all..

After I ran through my first tank of dealer provided gas - I filled up with regular. Immediately I noticed a performance issue - not only was the car a bit sluggish - the MPG average (after reset on fill up) was way lower -- and was lower while driving.

Like to get your opinion on fuel for the hemi based on your experience. What are you guys putting in and what is your experience...

Subsequently - I ran the tank to half and put in premium - effectively having a full take of a mid range octane... The car ran much better (still not as good as when I picked it up with dealer gas)... Maybe the gas I got at second fill up was sub parr - it was from Sams club - Ive never had problems there.

Thanks! Appreciate your advice. I know what the manual says - looking for your opinions and experience...
Owners Manual States 89+
 

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Discussion Starter · #4 ·
I bet most dealers only put 87 octane in the WK2, no matter what engine it has in it.
Agree - in fact it was the dealer who told me they use regular when I went to get my plates - and - that is what they suggest. Not what I found out to be true - at least not with that fill up...
 

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Trying to figure out how each tank of gas is reacting in a brand new vehicle is an exercise in futility. Maybe after a few thousand miles on the car you can detect something. The difference you realize could be from the gas, could be from the drive train going through various stages of break-in, could be you adjusting your driving to a new vehicle, and a good dose of "It's all in your head".

Use the gas the manual recommends - 89 octane. Now, forget about mileage for awhile and just enjoy your new ride. :)


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Discussion Starter · #8 ·
Trying to figure out how each tank of gas is reacting in a brand new vehicle is an exercise in futility. Maybe after a few thousand miles on the car you can detect something. The difference you realize could be from the gas, could be from the drive train going through various stages of break-in, could be you adjusting your driving to a new vehicle, and a good dose of "It's all in your head".

Use the gas the manual recommends - 89 octane. Now, forget about mileage for awhile and just enjoy your new ride. :)


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agree fully! its probably all in my head also! next tank will be 89
 

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So far I only fill up with 89. The dealer put 87 in the tank when I took delivery, but I hardly notice the power difference and what little I felt was probably in my head as suggested.
 

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So far I only fill up with 89. The dealer put 87 in the tank when I took delivery, but I hardly notice the power difference and what little I felt was probably in my head as suggested.
Manual says 89 octane. Anything higher is a waste. Not 87, not 91, not 93, just 89 lol.
 

· Lifer: Old Geezer
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agree fully! its probably all in my head also! next tank will be 89
It could also be related to the local altitude and the gasoline area you drive in.

At higher altitude, 87 is the midgrade [pump method].

If you are around LA, I have no idea what sort of witches brew they put in the gas there, but it drives like [censored], and the premium seems worse than the regular.
 

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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?
 

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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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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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idk about the swag method..

anyways I have always run Shell 93 octane. she seems to love it.
 

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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.
 

· Lifer: Old Geezer
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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.
 

· Lifer: Old Geezer
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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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