6.4l- 87 vs 89 vs 93

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coobie

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87 oct in my 6.4 also.Tried 89 oct for 3-4 tanks noticed no difference :)
 

Andrew09HEMI

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You won't notice a difference from 87 to 89, try 91/93 and see if you do. I did so I'll continue using it. If you don't, don't use it.
 

Sandbox

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The Owners Manual for my 2017 states, "89 recommended, 87 acceptable". I ran 89 for the first 2 fill ups. Have been running 87 since.
 

14RAM4X4

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Ran 87 for ~80K miles in my '01 Jeep Cherokee 4.0, ~50K miles in my '03 F150 4.6, ~140K in my '08 Jeep Wrangler unlimited 3.8, ~26K miles on 2014 Ram 1500 5.7, and ~8700 miles in my 2015 6.4.

In all honesty, I haven't ever noticed any negative effects of running 87 and only noticed a positive difference in the F150 4.6. It liked 91 octane. But, then again, I had her tuned and skinny pedaled her all the time.

The only exception to this was my 1st 2 vehicles. A 75 cutlass with about 180K on the OD an 84 K5 Blazer with well over 90K (the OD broke at 90K and I drove it for 3 years after that). Both engines would start to knock a bit. So every so often, I'd run a few tanks of 91 and Lucas or Seafoam in the 1st tank. After 3 or 4 tanks the knocking went away and I'd go back to 87.
 
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Rampant

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The Owners Manual for my 2017 states, "89 recommended, 87 acceptable". I ran 89 for the first 2 fill ups. Have been running 87 since.

Interesting. The owner's manual for my '16 states -

"6.4L Engine
This engine is designed to meet all emissions regulations and provide satisfactory fuel economy and performance when using high quality unleaded gasoline having a posted octane number range of 87 to 89 as specified by the (R+M)/2 method. The use of 89 octane “Plus” gasoline is recommended for optimum performance and fuel economy.
While operating on gasoline with an octane number of 87, hearing a light knocking sound from the engine is not a cause for concern. However, if the engine is heard making a heavy knocking sound, see your dealer immediately. Use of gasoline with an octane number lower than 87 can cause engine failure and may void or not be covered by the New Vehicle Limited Warranty."
 

mtofell

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Interesting. The owner's manual for my '16 states -

"6.4L Engine
This engine is designed to meet all emissions regulations and provide satisfactory fuel economy and performance when using high quality unleaded gasoline having a posted octane number range of 87 to 89 as specified by the (R+M)/2 method. The use of 89 octane “Plus” gasoline is recommended for optimum performance and fuel economy.
While operating on gasoline with an octane number of 87, hearing a light knocking sound from the engine is not a cause for concern. However, if the engine is heard making a heavy knocking sound, see your dealer immediately. Use of gasoline with an octane number lower than 87 can cause engine failure and may void or not be covered by the New Vehicle Limited Warranty."

I seem to remember when this was discussed once before that the language in the manual changed slightly at some point. I think it pretty much says the same thing though. 87 is "acceptable."

I'm with many others - don't really notice a difference with 89 so usually don't run it. I will fill with 89 when towing my 11K 5th wheel. Again, can't say I notice a difference buy hauling 11K with a gas engine I need every advantage I can get. :favorites13:
 

SHOOT2KILL

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Wish I could find some ethanol free 87

Trust me...Your not missing anything...I experimented with 87 pure gas since I have a station 1 mile from home...Absolutely NO noticeable difference in performance....BUT...It did LOSE 1+ mpg during 3 different fill-up tests...My 6.4 runs best on Exxon/Mobil 87 for non towing...Their 93 octane does help the truck run better when towing and will give maybe 1.5 mpg better mileage. BUT, not worth the added expense IMO

Currently around here the e-free gas is 0.17 MORE per gal than the 10% ethanol fuel...

Also around here the 91/93 octane runs anywhere from 0.50-0.70 additional per gallon compared to the 87 depending which branded station you go to....
 
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Rampant

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My truck is not a daily driver. I do drive it at least once a week and usually highway for at least 50 miles. I've never ran anything besides 89 from Shell or Exxon/Mobil or ethanol-free 89 and I'm happy with it. Didn't notice any difference at all with the ethanol-free in the 5 or so times I've ran it.

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BIGWHITE16

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I ran 87 first cause that's what the dealer put I then I filled with 93 and there's a noticeable difference. Not night and day but if you're paying attention to idle, mds activation and slight throttle response it's definitely there.

BIG difference.
 

VicViper

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The manual on my 14' 6.4 says 87 recommended, but post 14' 6.4's are slightly different because of a wristpin problem on a batch of earlier 2014's. I guess they made a point to help get rid of "hemi tick" by suggesting people stay with 89 octane which the motor was designed for. Post 14' manuals state 87 is "acceptable" but not recommended. Also 87 may retard timing so you will lose power and fuel economy.


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JLEONARD

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I ran 87 when I bought this truck in December. I was hearing too much valve train chatter consistant pre-ignition so I started running 89, same deal. Now I run minimum of 91 and it seemed to have cleared up. That being said I feel no power gains nor is my mpg different, just runs smoother.
 

VicViper

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ugh...I am really going to hate filling up with 93 from now on...JLEONARD I get the same sounds from my motor...

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PatinAZ

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91 is the highest in my parts. I switched to running it over 89 when I noticed I was getting 20-30 more miles per tank and the truck just seemed to run better with 91. For a few bucks more per fillup, I'm good with it.
 

Mchurch52

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I run 89 octane in mine day to day with a Hemifever 87/89 tune. When 93 octane goes below $2.50 per gallon, like it is right now, I'll put that in with a HF 93 octane tune. The engine runs noticeably smoother and stronger on 93 octane, but again, that is because I am using a tune optimized for 93 octane.
 

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