Hemi 6.4, gasoline. 87 or 89.

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Rwgarrison23

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I filled up using both gasoline from Shell fuel. I ran 87 and 89. I dont know if it's me but truck seem to like 89 better. What is recommended gasoline for these 6.4? Mines a 2018, by the way.
 

tjfdesmo

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When I had my 6.4 I never saw a lick of difference, even pulling heavy, 23,160 lbs combined. Plus, the RV pumps have diesel and regular, so that's what she got.
 
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Rwgarrison23

Rwgarrison23

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I'll drive it a few days and see if I notice any difference going back and forth to work. Towing, definitely I'll use 89.
 

G. Mcpherson

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When I had my 2016 6.4 I used 89 to start with. Later went with 87 and used it most all the time except when towing.
 
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Rwgarrison23

Rwgarrison23

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Also sea level area. I think I'm at 3600 feet above sea level
 

mtofell

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Oh God..... not this again. Last time I think this went about 20 pages.

Cliff notes:

-Read the manual.
-89 octane "may" give a slight improvement in performance and MPG gain but usually not enough to offset cost
-Some swear there is an increase in towing power but those same folks also believe in ghosts.

Honestly, I have run a few tanks of 92 octane non-ethanol and gotten pretty good MPGs and power but I think it's more to do with the absence of ethanol rather than the octane. I only run that fuel due to camping deep in the woods and having only one type of fuel available. Otherwise, it's 87 octane regular.
 

Iron Outlaw

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You know I've ran 87 for over a year straight in mine and coincidentally today I filled up with 89. I swore to myself the midrange felt noticeably healthier on the way home.
 

Ribtipram

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We all know 93/91 is harder to burn then 87 or 89 right. Its a Compression thing. Run the lowest you can unless she spark knocks. Then bump it up one grade. Most likely the 6.4 will never ping off 87 unless its crazy hot out and pulling a heavy load(maybe). Mtofell is right the Absence of ethanol will always bring a couple of mpgs more.anything more then 89 for are 6.4's is a Waste of money.
 

SouthTexan

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The difference between the two octanes may be more noticable in hotter weather. The engine probably doesn't pull that much timing due to knock with outside temps being in the 70s as it would when outside temps are in the 100s. This may be why some people feel the difference and other don't.
 

stoney

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The difference between the two octanes may be more noticable in hotter weather. The engine probably doesn't pull that much timing due to knock with outside temps being in the 70s as it would when outside temps are in the 100s. This may be why some people feel the difference and other don't.

I was thinking the same as I read this.
The summer heat and added weight being towed during those months would justify the premium fuel, this is what I do, use premium in the summer when towing, when I'm guessing most with the gas engines usually tow heavier.
As for feeling the difference, the way these truck "learn" as you drive and react so differently, I wouldn't be surprised if the difference some folks feel is just that vs the fuel.
 

SouthTexan

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Ethenol is actually an octane enhancer so ethonal blended gas will have greater anti-knock properties than pure gas. Although your fuel mileage will suffer slightly due to lower energy content.
 

GsRAM

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You know I've ran 87 for over a year straight in mine and coincidentally today I filled up with 89. I swore to myself the midrange felt noticeably healthier on the way home.
Placebo effect probably....just as my engines always seem more quiet to me after i change the oil and filter.

I have been running 87 now all the time for over 2 yrs and have no issues. I feel no difference 87,89,93 except a lighter wallet on the latter two.


Running empty, towing heavy in the heat of the summer, anytime. No detonation at all, just good power and a smile on my face. LOL
 

McBroom

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I run 87 when not towing. 93 I I’m on a road trip or pulling a trailer for a long trip
If I’m gonna be off roading then it’s 93 again

The Blue Mule
 

SouthTexan

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I wonder how much power you actually gain from using 89 octane. I know in my old Ecoboost 3.5L F150, power went from 365 hp on 87 octane to 385 hp on 91 octane according to Ford. Not that much of a difference, but then again how much would it cost to get 20 hp with aftermarket mods especially in an N/A engine where it would cost you around $400 just to get a 30 hp bump with a tune.
 

Graygoose

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I wonder how much power you actually gain from using 89 octane. I know in my old Ecoboost 3.5L F150, power went from 365 hp on 87 octane to 385 hp on 91 octane according to Ford. Not that much of a difference, but then again how much would it cost to get 20 hp with aftermarket mods especially in an N/A engine where it would cost you around $400 just to get a 30 hp bump with a tune.
20hp is a lot, if I buy something 395, 400, 485, I want to use every ounce of power it makes...not worth the weaker gas to me.
 
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