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  #13  
Old 06-19-2011, 12:54 AM
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Re: HEMI: Getting +1.5mpg better with use of Regular Unleaded (87).

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Originally Posted by chuckbernard View Post
Could be worth trying out. There is a clear possibility that the software sets up the engine in a less-than-optimal configuration when using a higher octane.
The above manual quote specifically states 89 (mid-grade) for optimum performance. 87 doesn't provide optimum performance which should mean less MPG, not more. Regarding 91+ (premium) doesn't give any additional benefit beyond what you get with 89.

Many other people have posted with regard to the WK V8 Hemi that 89 gets better MPG than 87. The same should hold true with the WK2 V8 Hemi. Whether the additional MPG using 89 offsets the additional cost of 89...depends on gas prices.
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Old 06-19-2011, 06:55 AM
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Re: HEMI: Getting +1.5mpg better with use of Regular Unleaded (87).

In Australia our lowest RON fuel is 91 with 10% Ethenol, we then have premium 95 and ultra 98. All my cars run on 98 which costs 16c p/l more than the 91. I wonder if Jeep have retuned our cars to run on the 91, as I just expected the Hemi to need 95>. I cannot find the recommended RON for the Au spec ones, the V6 is Flexfuel ?
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Old 06-19-2011, 07:19 AM
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Re: HEMI: Getting +1.5mpg better with use of Regular Unleaded (87).

ENFORCER,

Octane ratings for the US vs. other countries are different. 91 RON = 87 US. Here's a converter: http://www.csgnetwork.com/octaneratecalc.html
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Old 06-19-2011, 07:51 AM
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Re: HEMI: Getting +1.5mpg better with use of Regular Unleaded (87).

I had the opposite results. I got better mpg with 89 vs. 87 octane. Perhaps you switched at just the time of year when your local station switched from winter blend to summer blend. Most states dictate some type of oxygenation additive in winer months which generally lower mpg and power output. If you switched from winter blend 89 to summer blend 87 you may well have gotten better mpg.
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  #17  
Old 06-19-2011, 07:56 AM
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Re: HEMI: Getting +1.5mpg better with use of Regular Unleaded (87).

I switched to 87 a couple of months ago, primarily due to the lower price at the pump. I don't drive my GC very hard, and really haven't noticed any difference in sound (no pinging) or performance.
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Old 06-19-2011, 08:30 AM
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Re: HEMI: Getting +1.5mpg better with use of Regular Unleaded (87).

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Originally Posted by Nouveau Redneck View Post
I had the opposite results. I got better mpg with 89 vs. 87 octane. Perhaps you switched at just the time of year when your local station switched from winter blend to summer blend. Most states dictate some type of oxygenation additive in winer months which generally lower mpg and power output. If you switched from winter blend 89 to summer blend 87 you may well have gotten better mpg.
Same here...

I've gotten consistently better fuel economy (albeit as reported by the EVIC) since switching from 87 to 89. Admittedly the increase has been just a couple MPG, but at nearly $4.00 per gallon here in the midwest I was willing to take what I could get.

My Hemi now has almost 4000 mi on the odometer so maybe now there would be no difference in economy by switching back to regular from mid-grade fuel. The vehicle runs great and performs as well as one could reasonably expect from a 5000lb SUV with the 89 octane fuel so I'll keeping using it.
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Old 06-19-2011, 09:27 AM
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Re: HEMI: Getting +1.5mpg better with use of Regular Unleaded (87).

Quote:
Originally Posted by ENFORCER View Post
In Australia our lowest RON fuel is 91 with 10% Ethenol, we then have premium 95 and ultra 98. All my cars run on 98 which costs 16c p/l more than the 91. I wonder if Jeep have retuned our cars to run on the 91, as I just expected the Hemi to need 95>. I cannot find the recommended RON for the Au spec ones, the V6 is Flexfuel ?
Yeah, it would be interesting to hear which is better.
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