Regular, Plus or Supreme Gas in the 6.4 Hemi

[CanadianRAm16]

Just wondering what people are running in their 2500 6.4 Hemi. Anyone notice or getting better fuel mileage or better engine performance with a higher octane fuel??

 

[Hootbro]

Question has been asked a bazillion times.

Cliff notes is the engine adjusts the timing and makes slightly less HP with 87 octane and is fine for most people in daily driving styles. If you run the engine to it's max limits when towing or hauling, then 89 octane shines.

As to MPG gains for daily driving, the premium costs for 89 over 87 octane does make sense in the math for very little if any MPG gains. What little anecdotal evidence people have provided has not shown any financial benefit of using 89 octane over 87.

There is absolutely no benefit for using fuel premium 91-94 octane gas other than a lighter wallet.

99% of any MPG economy gains will rest on your driving style with this engine.

 

[dkmesa]

Question has been asked a bazillion times.

Cliff notes is the engine adjusts the timing and makes slightly less HP with 87 octane and is fine for most people in daily driving styles. If you run the engine to it's max limits when towing or hauling, then 89 octane shines.

As to MPG gains for daily driving, the premium costs for 89 over 87 octane does make sense in the math for very little if any MPG gains. What little anecdotal evidence people have provided has not shown any financial benefit of using 89 octane over 87.

There is absolutely no benefit for using fuel premium 91-94 octane gas other than a lighter wallet.

99% of any MPG economy gains will rest on your driving style with this engine.

Very well said. The only caveat I will make is that premium 91 or 93 octane has it's performance benefits IF the truck has been tuned for that octane rating.

 

[Hootbro]

Very well said. The only caveat I will make is that premium 91 or 93 octane has it's performance benefits IF the truck has been tuned for that octane rating.

Agreed. Custom tunes is whole another topic though.

 

[smurfs_of_war]

I use 87 across the board even when towing. 89 isn't an option in our farm tanks so I've never used anything else with this engine.

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[MN-Ram]

I drove the first 22,000 miles with pretty much only 89 octane, and the last 2,500 miles with pretty much only 87 octane. The mpg drop was maybe 0.5-1mpg just driving around. Not worth the extra $0.20-0.30/gallon for me. But I'm at roughly 1,000FT of elevation. I don't know if that matters at all with these engines.

 

[Dmopar74]

Mine runs like doo doo on 87

 

[mtofell]

I drove the first 22,000 miles with pretty much only 89 octane, and the last 2,500 miles with pretty much only 87 octane. The mpg drop was maybe 0.5-1mpg just driving around. Not worth the extra $0.20-0.30/gallon for me. But I'm at roughly 1,000FT of elevation. I don't know if that matters at all with these engines.

Around my area the difference only about .15 - some stations only a dime. I just ran some numbers and @ .15 the break even is somewhere between .5 and 1MPG needed in order to have the mid-grade pay for itself.

I started running mid-grade for towing season and can't say I really notice a difference but it's hard to say. Overall, this truck hauls my 10K 5th wheel just fine. I don't micromanage my MPGs but what you say sounds reasonable.

 

[dexter]

If you run the engine to it's max limits when towing or hauling, then 89 octane shines.

I'm guessing it would take awhile for the computer to adjust to 89 octane. If so, how many tanks/miles do you think it would take?

 

[mtofell]

I'm guessing it would take awhile for the computer to adjust to 89 octane. If so, how many tanks/miles do you think it would take?

I think it's pretty much instant. The computer knows the octane and adjusts to what it's being fed.

 

[DannyMK2]

daily driving unloaded i cant tell a difference between 87 and 89 so i run 87. towing heavy i would run premium.

 

[MN-Ram]

Around my area the difference only about .15 - some stations only a dime. I just ran some numbers and @ .15 the break even is somewhere between .5 and 1MPG needed in order to have the mid-grade pay for itself.

I started running mid-grade for towing season and can't say I really notice a difference but it's hard to say. Overall, this truck hauls my 10K 5th wheel just fine. I don't micromanage my MPGs but what you say sounds reasonable.

If the difference in price was only $0.10 (which it used to be a couple of years ago) I would probably run 89 all of the time. Just driving around town, I don't notice anything different between the two. I still run it if I have to tow, which is rare. I bought the HD for payload when I cut firewood, and occasional towing.

 

[craigsez]

I know there is no performance gains and i dont really worry about mpg cause i drive long haul truck and it usually takes me a month to burn a tank of gas..
Lately i have been useing 91 vs the 89 and it seems to run a lil smoother,power wise i dont see a diff,mpg awww well i dont get to drive it much so its not an issue...I will say im almost 100% sure i was hearin a wee bit on a fuel knock at low rpm till she got up a lil then i didnt hear it,with 91 i never hear it and my truck has nooo engine mods..

Oh and i live near sea level here in eastern canada..

 

[River19]

I have run both 87 and 89 since I have owned the truck and I would like to believe it runs smoother on 89, but I have no real proof personally. When I tow, I fill it up with 89 and run only 89 during the towing season as the cost difference doesn't make much difference to me as I don't put too many miles on this rig each year, maybe 7000 miles per year.

 

[WaterBoy1]

I've run 87 since the truck was new 18 months now. No problems at all. I think my lifetime fuel mileage is pretty decent (fuelly)

 

[Bigdaddy]

I have being putting 87 octane in mines since I had it, so I try putting 89 octane and this is all hand calculation but the mileage did change so I went back to 87 octane. The dealer said that I can use 87 octane but I only believe half to what they say so I try it anyway but it didn't change.

 

[Hootbro]

I think it's pretty much instant. The computer knows the octane and adjusts to what it's being fed.

I'm guessing it would take awhile for the computer to adjust to 89 octane. If so, how many tanks/miles do you think it would take?

What mtofell said, pretty much the nanosecond the knock sensors detects any pre-detonation (knocking) or lack of, it will retard or advance the timing and fuel trim as needed to compensate within reason. Your "butt dyno" will probably never know the transition.

As to how many tanks? it will take a couple or more to be true 100% 89 octane and will depend on how much is left in the fuel tank of 87 octane when you fill up. The less left the better.

 

[THETANK]

I run 110 octane in mine, nothing changed over the 87.

 

[Rampant]

I run 89 non-ethanol. 17.4 lifetime mileage.

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[68PowerWagon]

I run 89 non-ethanol. 17.4 lifetime mileage.

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Wow! That's great mileage. That's the problem with ethanol & E-85. It is a little cheaper & supposedly better for the environment but if it takes more of it to do the same task I don't see how that benefits anything. I know when I run E-85 in my Durango I lose 4-5mpg. I usually don't bother to buy it unless it is 20+ cents cheaper/gal.
There are a lot of areas (especially in the mid-west) that offers only 10-15% ethanol. It would be nice to have a choice.