What fuel do i use?

[PCT]

The dealer gave me the wrong instruction manual. They gave me a diesel. What fuel does the 6.4 take? I have been putting 87 in it.

 

[RainDesert]

I ran 87 in my 6.4

 

[MADDOG]

I ran 87 in mine until I tuned it, then I switched to 92.

 

[RBinNC]

The manual says you can run 87, but 89 is the preferred gas for it.

 

[Wadejesu]

Hey Maddog, what tune?

 

[PCT]

Does anyone notice a difference between 87-89?

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[redman4455]

Does anyone notice a difference between 87-89?

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I'm not sure about the 6.4, but my 08 5.7L I do notice slightly smoother running engine when using 89. Truck is a bit old though and the cat is starting to go so I dont know if that contributes to anything.

 

[Ratket]

Hey Maddog, what tune?

@MADDOG

 

[MADDOG]

Hey Maddog, what tune?

I used a DiabloSport I2 programmer and had HemiFever build me a custom tune.

 

[Trailmaker]

The manual says you can run 87, but 89 is the preferred gas for it.

True.

Does anyone notice a difference between 87-89?

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@PCT yes especially for Eco mode. The guys that complain about the vibration with MDS activates... the 6.4 is programmed to run on every other cylinder (4 at a time) with higher octane because of the speed up timing.

 

[RBinNC]

True.



@PCT yes especially for Eco mode. The guys that complain about the vibration with MDS activates... the 6.4 is programmed to run on every other cylinder (4 at a time) with higher octane because of the speed up timing.

I run 89 and it still vibrates. I've also run 93, and it still vibrates. Dealer replaced active noise dampeners....you guessed it, still vibrates.

 

[Mega-Hemi]

I run 89 and it still vibrates. I've also run 93, and it still vibrates. Dealer replaced active noise dampeners....you guessed it, still vibrates.

Mine vibrates on 89 too. Only 170 miles on it so far so hoping it will get better as it breaks in.

 

[RandomRam]

At 1000 miles mine has noticeably smoothed out.

 

[Johnny Ram]

So if I'm cutting off MDS by putting it in 8th gear right away ... I can run 87 without any issues ? It's like 60 cents less per gallon than 93 ... so figuring the decrease cost in gas will cancel out the lost benefit of MDS fuel efficiency and I don't have to be driving around annoyed all the time with a vibrating motor. I was thinking about running 87 like 80-90 % of the time and dumping some 93 in there every once in a while to bump up the average octane in the tank a little bit ... any concerns with this strategy ?

 

[Punishher7]

So if I'm cutting off MDS by putting it in 8th gear right away ... I can run 87 without any issues ? It's like 60 cents less per gallon than 93 ... so figuring the decrease cost in gas will cancel out the lost benefit of MDS fuel efficiency and I don't have to be driving around annoyed all the time with a vibrating motor. I was thinking about running 87 like 80-90 % of the time and dumping some 93 in there every once in a while to bump up the average octane in the tank a little bit ... any concerns with this strategy ?

MDS is negligible at best ref fuel economy. The 6.4 runs just fine on 87. The only reason to run 89 is if you want the advertised HP/TQ at the crank. Again, a negligible difference. Save yourself a little cash and run 87.


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[Trailmaker]

So if I'm cutting off MDS by putting it in 8th gear right away ... I can run 87 without any issues ? It's like 60 cents less per gallon than 93 ... so figuring the decrease cost in gas will cancel out the lost benefit of MDS fuel efficiency and I don't have to be driving around annoyed all the time with a vibrating motor. I was thinking about running 87 like 80-90 % of the time and dumping some 93 in there every once in a while to bump up the average octane in the tank a little bit ... any concerns with this strategy ?

The 19 is more forgiving if you run mid grade then the 6speed in the last generation. it is a 0.30 difference and 2-3 mpg better in eco.
I don’t have a dog in the fight so I’m not going to argue with anyone about saving gas or being annoyed with mds on and saying the truck runs okay with reg unleaded. I guess all we have, is a personal experience and manufacturers recommendations.
I run 91 and never turn off mds.

 

[RandomRam]

Im at 1300 miles on my 6.4. The MDS vibes have mellowed considerably. It was pretty obvious when new, now it’s not. I’ve only been running 87 octane but now I’m curious. I’ll let the tank go to the gas light comes on and will fill with 89. It’s only 10 to 15 cents more a gallon here. If I gain 1 mpg it’ll be even since I’ve only been averaging 13.

 

[Travelin Ram]

I’ve been running 89 for break in, since my preferred method is to air it out from time to time to seat the rings and I want 100% of the rating for that.

After 1k miles I’ll probably go to 87. All modern engines are running dynamic timing maps so the result is it’s just going to retard the timing slightly from the knock sensor feedback. Probably lose an imperceptible amount of hp.

 

[Truckin19]

I run 89 per manual recommendations. Seems to do just fine.....

 

[star_deceiver]

89 from the Mobil station or 91 from Costco are almost always 1c/L difference so I fill up at the station with the shortest line.
The few tanks that I’ve used 87 seem to make the MDS transition more abrupt and the engine a little less enthusiastic, at least in my mind.