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-   -   89 octane for 5.7 Hemi recommended? (http://www.jeepgarage.org/f109/89-octane-for-5-7-hemi-recommended-41939.html)

gaidin43 05-10-2012 08:07 AM

89 octane for 5.7 Hemi recommended?
 
I was reading the manual and I noticed 89 octane is recommended for the 5.7 Hemi but 87 octane is acceptable.

What are people's thoughts on this? I've always used 87 octane in all my vehicles. I'm not sure how much of a performance increase or mpg increase I'd get for the increase cost of price per gallon.

bmrisko 05-10-2012 08:15 AM

Re: 89 octane for 5.7 Hemi recommended?
 
I use the recommended 89. An extra $2-$3 per tank isn't going to kill me.

BuckeyeSRT 05-10-2012 09:51 AM

Re: 89 octane for 5.7 Hemi recommended?
 
Very common topic here. Try a search and you will see.
Enjoy your Hemi!

77rednecktruck 05-10-2012 10:36 AM

Re: 89 octane for 5.7 Hemi recommended?
 
I fill it with 89 and my wife fills it with 87 when she drives it. I notice no difference either way.

gaidin43 05-10-2012 10:55 AM

Isn't it ill-advised to switch octanes back and forth?

So what I'm reading it advised to use 87 in winter and 89 in summer?

peckmv 05-10-2012 11:23 AM

Re: 89 octane for 5.7 Hemi recommended?
 
All 89 does is add more anti-knock. It does nothing for mileage. I run 87 all the time with no issues. I do run 89 when I tow. This is because the added strain of the towed load causes the timing to advance and without the added octane knocking will occur, when going up hills.

rushdriven 05-10-2012 10:52 PM

Re: 89 octane for 5.7 Hemi recommended?
 
I usually fill up at Costco since there is one appox. 3 miles from my house. My only choices there are 87 and 91 octane. I always fill it with 91 octane. When I get as at other stations, I use 89. I seem to get a little better mileage with 91.

djva076 05-10-2012 10:54 PM

89 was recommended, and that's what I use. What a lot of people don't realize is that the octane ratings in gas indicate how stable the fuel is under heat and pressure and you don't just select it for better fuel economy.

Higher octane gas remains more stable under a given amount of heat and pressure than lower octane does. Hot running engines with high compression ratios NEED higher octane gas so that it won't detonate before the engine finishes compressing the air and fuel mixture anand feeds it a spark.

Using higher octane fuel in a car that calls for 87 just makes your car have to try and adjust timing for proper detonation. Using lower octane fuel than recommended for your engine makes it run the risk of dealing with fuel that will likely detonate prematurely until/if the computer adjusts timing.

Be nice to your engine and computer and just use whatever the manufacturer says is OK.

Just my 2

-D-

Sent from my GT-N7000 using Tapatalk 2

Jdsmitty10 05-11-2012 08:35 AM

Re: 89 octane for 5.7 Hemi recommended?
 
To me, if it calls for 89 but 87 is ok.. using 89 probably gets you the max HP/torque advertised for that engine...running 87 maybe not? im probably wrong...

djva076 05-11-2012 12:35 PM

Quote:

Originally Posted by Jdsmitty10 (Post 627976)
To me, if it calls for 89 but 87 is ok.. using 89 probably gets you the max HP/torque advertised for that engine...running 87 maybe not? im probably wrong...

Yeah, I hear ya. That's probably the reason for the recommendation. I'm not sure what the long-term implications would really be of running on fuel that isnt recommended, but is still supported (to an unstated extent).



Sent from my GT-N7000 using Tapatalk 2

CIEGOS 05-11-2012 12:40 PM

Re: 89 octane for 5.7 Hemi recommended?
 
I always find it ironic that people who get the 5.7L don't worry about how much gas it consumes but rather what octane to put in their gas guzzler in order to save money. If you can't afford the extra 5% more in cost maybe the v6 is more up your alley... just saying :)

Yadkin 05-11-2012 12:46 PM

Re: 89 octane for 5.7 Hemi recommended?
 
I've had a vehicle before where the OM recommended 89 and had very poor luck with fuel consistency. Apparently stations get 87 and 91 delivered in separate tanks then mix the two at the pump to make 89. So I usually ended up buying 91. I hated having to toss that money out the window so traded in the car.


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