87 or 89 octane

[Bamacommander]

Just bought a new Ram Bighorn with the 5.7 Hemi. I was looking at the online owners manual and it said 89 octane was recommended but 87 octane was acceptable . Which one should I use? I have used both at different times and can not tell the difference. Any suggestions?

 

[Jrod]

I'm on my third RAM 5.7. I've always used 87 octane without issue.

 

[Ohio5pt7]

I've used 87 for 41k miles in my 18 no issues

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[Graygoose]

89. While it will work on 87, anytime you push the skinny pedal hard to pass, or tow, the engine may detonate, or retard timing due to detonation, aka loss of power.
Me, I'll pay for 89 and not worry about detonation.

 

[TheKenster]

89. While it will work on 87, anytime you push the skinny pedal hard to pass, or tow, the engine may detonate, or retard timing due to detonation, aka loss of power.
Me, I'll pay for 89 and not worry about detonation.

Same. I've always used 89

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[gustheram]

I ran 87 for 67k miles in my 15 6.4L and I've run nothing but 87 in my 19 5.7L (only about 1200 miles so far). No problems with it in either truck so for the ~$.30/gal difference in my area, I stick with 87. The price difference works out to about $10/tank, which isn't much but it adds up over time so I'll keep the money lol.

 

[Graygoose]

I ran 87 for 67k miles in my 15 6.4L and I've run nothing but 87 in my 19 5.7L (only about 1200 miles so far). No problems with it in either truck so for the ~$.30/gal difference in my area, I stick with 87. The price difference works out to about $10/tank, which isn't much but it adds up over time so I'll keep the money lol.

I thought the 6.4 only recommended 89 and up?

 

[turkeybird56]

Same. I've always used 89

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89, if I am topping off just fer chits and giggles I may throw $5 or $6 of 87, but generally stay with 89. On MY 2012 Hemi, when I ran 87, it pinged everywhere. Not so much with the MY 19. BUT U gonna get a 1,000 different opinions. Put in what works for U...

(SIDELINE: My Honda Goldwing calls for 87, but I have to run 89, cause that V6 motor (yes for those not know Goldwings have 1833 V6 motors), just runs like a dog on 87, I know totally unrelated, lmao)

 

[arod412]

When I had my 2012 5.7hemi, I mostly ran 89....but obviously some situations I throw in a couple dollars for 87. Nothing major after 35k miles...but again, you can feel the different when you step on the skinny petal.

Former owner of a Ram 1500, Current owner of a Dodge charger scat pack, possible future owner of a jeep gladiator.

 

[shmedley]

89 is what I normally put in it. When I know I'm going to be towing I put 93 in it.
I figure the piece of mind is worth more then the 5.00 or so difference for a full tank

 

[Mandride]

I have been researching and testing mileage related to Octane. So far it can be a wash as you do increase mileage based on octane for daily driving. Once I am done with my testing in comparison of daily driving and also towing RV driving I will share the results. So in reality if you get a reasonable price for 93 verse 87 you win by performance increase. Once I get enough miles under the trucks belt I will post results.

The interesting one was with My GMC 5.3 that would run E85. Extra 25 HP with E85 but mileage went from 20 to 12 and it was about a .75 cheaper from 2.25 to 1.50 per gallon so didn't wash out for me. Plus harder to find and had to fill up too much, but 20 hp can be noticed.

 

[autumnwalker]

I ran 87 in it until one day I heard it ping. 89 ever since.

 

[gustheram]

I thought the 6.4 only recommended 89 and up?

For 2014, the manual said only 89. In 2015, they revised it to say the same thing the 5.7 says: 89 recommended, 87 acceptable. Not sure if they changed it again later, but I never had any problems running 87 in mine. In FL, 87 is the lowest grade. When we went north a few times, I saw 85 as low grade and 87 as mid grade. In that case I always went to the 87 mid grade still. Not sure if elevation maybe has anything to do with it, but I never heard any knocking or felt any power loss even all the way up at 4 and 5k RPM. I'm inclined to believe it doesn't simply because I never had any issues in the mountains of Tennessee either but who knows. Maybe mine just wasn't picky.

 

[corneileous]

Pretty much 89 in my 18’ Hemi. I’ve ran a few tanks consecutively of ethanol-free 87 in it here and there and even though I haven’t heard any pinging- in this one, or my old 08’ I had before, I keep going back to 89 because I can feel a difference. I can also see it in my fuel mileage.


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[corneileous]

89 is what I normally put in it. When I know I'm going to be towing I put 93 in it.
I figure the piece of mind is worth more then the 5.00 or so difference for a full tank

I wouldn’t use higher than 89 unless its been programmed to run that hot of fuel but that’s just me I spose.

Maybe things have changed in the last few years but usually the only thing a higher octane fuel does for you is just take a few more bucks out of your wallet.


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[Mike Murphy]

89 per the owners manual. Below that is an early combustion event because the fuel ignites easily (compression) and the pistons are not where they are supposed to be. 91 is hard to ignite with cylinder heat and ignition resulting in an even more incomplete burn. Meaning less energy to push the piston. Spark plugs are also sold in heat ranges. Hotter spark plugs and higher compression engines for high octane. Vehicle never burn all the fuel. Does it work? Absolutely! They all do. We are talking atoms here but there is a difference. Unused fuel also creates carbon on the valves, pistons, etc... overtime. Fuel is also a lubricant and coolant among many other things. Low octane burns sooner and all of it is gone meaning no coolant for the cylinder and valves. The combustion chamber heats up past effective threshold, the chamber can create NOX at 2500F which kill everything. 91 does not burn so easily meaning excessive coolant in the cylinder resulting in lower combustion chamber temperatures. Low temperatures do not like to burn which is why we used to choke our engines, to create operating temperature. Unburned fuel is wasted energy. An old school champion spark plug re14mcc4 for example.

R= resistor 6-15 k ohms E=14mm x 1.25 taper 14=Heat range this one is medium hot (1-23engines 53-63 is performance indycars 75-95 is industrial engines) MCC=electrode type 4=gap 1mm or 1.14mm or .045"

If the spark plug can not dissipate heat it may crack or prematurely fail. Excessive heat is transferred to the cylinder head and to the cooling system if it does not burn a valve. Now there is an effect on the cooling system...etc... If the cylinder is cold the plug will foul out. Again does it work, yes, yes it does but not to the best of its ability. Are there going to be variations, yes. Someone on here can school me on their application. What I show are industry standards and what billion dollar companies have engineers research. Although if they did it right there would not be mechanics...

 

[gustheram]

Hmm. Y'all got me thinking. I never noticed a difference on my 6.4L but I've never actually tried a tank in the 5.7. Maybe I'll run a few tanks through the 5.7 and see what I think. If it changes anything, I'll switch. If I don't notice a difference, 87 it is for me.

 

[dano66]

Shell premium all the way. No ethanol in it here where I live.

 

[tidefan1967]

Shell premium all the way. No ethanol in it here where I live.

That's the best there is but damn its expensive! Shell premium is like $1 more a gallon here!

 

[Judy]

87-just stay away from the ethanol is what is most important...... zero