Required octane for the 6.4?

[mazurekd]

Got my 2016 PW a few weeks ago. Laramie, very nice! It was my understanding that the 6.4 was fine on regular grade gas (87 octane). I was perusing the online manual, and it stated that both the 5.7 and the 6.4 recommended 89, though 87 was acceptable. I filled it a few times already with 87 octane, sounds fine, no knocking. So, I guess it is 'acceptable', but wonder if my performance and/or mileage may improve with the recommended 89 octane gas.

So, wondering what others are using, and if I can continue with regular grade. I understand the bigger 6.4 is a detuned 5.7, though obviously bigger. That being, regular should be fine in the 6.4.

Thanks.

 

[Rlaf75]

If the engine doesn't spark knock or "ping" then keep running the 87. If it does spark knock then bump up to the next octane. There's no real need to waste your money on the higher octane gas if you don't need to.

 

[Hootbro]

With the exception of one tank fill, been running 87 octane fuel with no issue. Unless I get some pinging under load to tell me otherwise, I will stick with the 87 octane stuff.

 

[gassersarentdead]

If the book.recommends 89, why wait for something to happen to change? When I had my gasser it never saw anything besides 89.

 

[theviking]

Mine ran fine with 87 octane but I would also say that the engine runs a bit harder on mid-grade/super. I would suggest at least trying it once and see if you feel any difference.

 

[Hootbro]

If the book.recommends 89, why wait for something to happen to change? When I had my gasser it never saw anything besides 89.

Because for "me", the 20-25 cent extra per gallon, no change in MPG and butt dyno telling me otherwise, the juice is not worth the squeeze to go to 89 octane.

 

[gassersarentdead]

I'm not a vehicle manufacturer, so I just listen to them. I wouldn't have the truck if I was pinching pennies either. Op I'm sure you'll be fine on 87, there's other threads on here with alot of people running it. Imo I'd go 89, you bought a nice truck why not treat it to some good stuff.

 

[stoney]

The computer will remove timing under load to reduce or eliminate knocking with a lower grade of fuel, so your motor will make less power.

I run 87 for day to day driving and 89 when towing. ....but to each their own.

 

[Am3gross]

OK, i am one of those guys that thinks gas stations rip you off, i feel that all the gas is the same and they only make you think you are getting better gas... with that being said...

i have done 87 on my 1st 2 fill ups.. 89 on my last one... on the 1st 2 fill ups i got 10.8 and 11. something, cant remember.. third tank with the 89 i will get 9.8... now that might have something to do with the winter mixture i dont know. i did not notice a performance difference as i try and keep my foot out of the gas to conserve that fuel till it is broke in...

now again because i feel the way i do about the gas stations, i will still put 89 in there and spend the extra couple bucks for the tank... maybe...

 

[loveracing1988]

I'm not a vehicle manufacturer, so I just listen to them. I wouldn't have the truck if I was pinching pennies either. Op I'm sure you'll be fine on 87, there's other threads on here with alot of people running it. Imo I'd go 89, you bought a nice truck why not treat it to some good stuff.

If you truly listened to them you would see that it doesn't say 89 is REQUIRED it say RECOMMEND. If running 87 had any detrimental effects it wouldn't say 87 was acceptable.
To the OP, for 2014 the same exact motor with the same power output said 87 was recommended, for 2015 they decided to change it to 89 with no explanation as to why.

 

[Hootbro]

I'm not a vehicle manufacturer, so I just listen to them. I wouldn't have the truck if I was pinching pennies either. ..........

I am not losing sleep over it.

 

[smurfs_of_war]

With 10:1 compression (which really isn't that high) a higher octane rating will allow a little more timing advance which translates into a bit more power. The beautiful thing about the systems controlling these engines is that they can sense the presence of pre-ignition or knocking/ pinging and compensate by pulling some timing to correct it- very simplified explanation, sorry. The result of that is a tiny loss in power, but no actual damage or detrimental effects.

I remember years ago when we used to build old iron horses with mechanical ignition and carbs and nothing but our ears. The only way to get the power without the pre-ignition was to time it correctly with the correct grade fuel and keep it like that. Never mind having to screw with things to match the witch-hat lobes on the cam, high comp pistons, whatever we decided might make a difference. That is my favourite sound to date- the sound of the 400 in my TransAm cammed to hell idling...

 

[gassersarentdead]

If you truly listened to them you would see that it doesn't say 89 is REQUIRED it say RECOMMEND. If running 87 had any detrimental effects it wouldn't say 87 was acceptable.
To the OP, for 2014 the same exact motor with the same power output said 87 was recommended, for 2015 they decided to change it to 89 with no explanation as to why.

Um.....post #4

 

[BossHogg]

Um.....post #4

All I will say is octane does not contain any heat energy therefore unable to provide you better MPG.

Try 87, you will save a few bucks and see no difference unless you are towing heavy in hot weather climates.

 

[loveracing1988]

Um.....post #4

What about it?

 

[hutchman]

From the owners manual:

"This engines 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. "

FWIW.....

And BTW, looks like a pretty good forum!!

 

[Bigdaddy]

Welcome hutchman from the Tacoma, WA area.

 

[mazurekd]

OP here. Thanks for the replies. Yes, good forum. Next tank I may try 89 octane to see if any changes, but in the mean time, I will not lose sleep using the "acceptable" 87 stuff. First fill up, regular was $1.79, mid grade was $2.59. As a percentage, that's quite a bump. It's not the money, my other car requires premium, and I have no issues putting the extra money in it. But if I really don't need to go up in the Ram, why?

Thanks all.

 

[RoadDog66]

I've run 87 and 89 in back to back fill-ups of 20 gallons+, same conditions, road, driving style. No discernible difference. I've also done the same towing a 7000 lb travel trailer, again negligible difference. I'm sticking with 87 as it it's perfectly acceptable according to Chrysler, so why waste the .25 cents/gallon.

 

[zeddy]

Since I bought my truck, i've been putting 87. This last few tanks, i've been putting 89. I've noticed a few things, one, when i used 87, my lieometer said i was averaging 10.6 MPG. With 89, i'm averaging 9.5 MPG. Driving habits are the same, I mainly do city driving, and no, i don't have a lead foot.

another thing i have noticed is the MDS. It seems like the MDS hates 87. When the MDS kicked on, the truck did sound like crap, vibrations, knocking. With 89, no vibration or knocking. So much smoother. I noticed a big difference.

Yeah, i'm getting less MPG, but can't complain. I didn't buy this beast for fuel economy.