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rjangel 05-13-2010 09:40 PM

New Hemi owner
Just picked up my '05 5.7L WK w/55K miles this evening, also have an 02 4.7L WJ with some tranny issues.

The 'book' recommends 89 octane fuel, but, the previous owner said he used 87 w/o any problems. Has anyone noticed a difference between using these to fuel grades? Does it improve fuel economy on the highway? I'm thinking to just use the 89 for the minimal (~3%) difference in cost?


SilverLimited 05-13-2010 09:50 PM

Re: New Hemi owner
You'll get a number of different recommendations on this question.

My $ .02 - have used 87 for approx. 95% of the 65,000 miles on my 05 Limited 5.7

Haven't had any operating issues. Personally changed the plugs 2 times, no noticeable plug wear problems. Probably saved about $450 or so over the years.

Scottina06 05-13-2010 11:21 PM

Re: New Hemi owner
congrats and welcome! You'll be modding soon and using 93 I would use what it calls for in the manual

cain45 05-14-2010 05:36 PM

Re: New Hemi owner
I use only 89 in mine as that's what Jeep states in the manual for "optimum performance." Congrats and welcome!!!!!:D

White Chocolate 05-14-2010 05:42 PM

Re: New Hemi owner
Welcome to JeepGarage

DJ BoNiOmArIo 05-14-2010 06:03 PM

Re: New Hemi owner

sanitarium16 05-15-2010 07:45 AM

Re: New Hemi owner
when i picked up my jeep the dealer said use of 89 will give better performance and fuel economy, using 87 will kick back the timing a little but can be used. I use 89.

rjangel 05-15-2010 10:12 AM

Re: New Hemi owner
Took a 350 mile road trip in it Friday to pick up my daughter from school.
Filled up w/89 for the way home and averaged almost 18mpg along the hilly west half of the PA turnpike on the return trip. That works for me.

ThankX all,

dmsfun 05-18-2010 01:23 PM

Re: New Hemi owner
use only 89 and only buy gas from a TOP TIER station, not discount gas; 87 will work in a pinch, but the ignition timing is retarded to prevent knock under load, power output is reduced, and mpg is worse than 89, plus 87 does not contain the same additives that keep from forming carbon deposits in the engine.

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