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Discussion Starter · #1 ·
Going to be hot for a while and wondering if running premium will help with performance as I am now running 315's and 3.73's. Thinking that the Pentastar will run at full potential and not retard power with the premium.
 

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Mmmmm...... Your money but with our compression, I'd say 87. That said, Under heavy load (towing, steep grades, etc) if it is really Hot.
Why not.
 

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Probably won't make any difference and you will be simply wasting money. Your engine was designed to run on 87. Higher octane simply helps prevent pre ignition (knock) and is required only in higher compression engines. The higher compression makes the power, not the higher octane gas.
 

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In order to see any gain from Premium fuel you must be tuned for it. Factory tune is for 87 octane.
91-93 octane requires the timing to be advanced.


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The only thing I know is the premium fuels from Exxon, Shell, Valero, and Chevron have a superior additive package and burn cleaner (so I have been told by refinery operators). As stated, spark advance and compression are the determining factor on octane requirements. Then you get into low compression ruining a blower which packs fuel / air into the cylinders.
Bottom line I run premium simply because of the detergents, nitrogen, and other premium additives, not because of the octane level.

I believe the computer controls spark advance these days based on what the engine is doing at any given time. I could be wrong on that. I can say fuel millage does not change regardless of what fuel I run at least on our Jeeps.

If I had my choice I would never run gasoline that had ethanol added. That's the real enemy..... Just my thoughts.
 

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Discussion Starter · #8 ·
Thanks for the answers. Now I will have more money for more mods.
 

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At least as far as Chevron is concerned all grades have Techron in it. You are not getting any better additives by going to a high fuel grade.
 

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Waste of money. Run 87.
 

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Discussion Starter · #11 ·
OK, 87 it is. I remember the old days when it mattered. 70 Bronco built 302 10:1 and 3/4 lift cam. These days are better.
 

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I've been running only 88 "clear gas" or ethanol free gas for the last few tanks. It's much easier on the fuel system, and I get about 1 mpg or more better, so it's worth it to me.

Yes, I know the Jeep's fuel system can handle the 10% ethanol in modern fuel. That's not the point, ethanol free is easier on the fuel pump and such parts.
 
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The way I see it, the world seizes to exist using 93% fuels 1,852,404 years from now and using 87% fuels it will last 1,852,403 years. I think all vehicles should be manufactured to run on one grade of gasoline, as 99% of them can do already. My wifes new Acura calls for 92% and my new Ridgeline calls for 87%, both have the same Honda 350 engine, one is 280hp and the other is 289hp, go figure on that one. So for 9hp I should spend $ .40 more per gallon at the pump, I don't think so.

trainman
 

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Discussion Starter · #16 ·
When I am in the JK I am not in a hurry to get anywhere and seldom hit close to 70 on the freeway. My Ram diesel will cruze at 75 like the JK does 55. The JK will seldom, if ever be more than 100 miles from home. 87 will be fine.
 

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The best summary from the article:

"In any event, to save money on gas and prevent straining your engine, follow the recommendations in the owner's manual. "
What's a manual?
 
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