$$$$$ to performance ratio wisewhats better reg or premium

 

assuming you have a hemi you are supposed to run 89 and thats how it performs best unless you get a tuner

 

Why a double post?... anyways.... Use 87... you will not gain anything by using 91 octane.... the 4.7 is NOT a performance engine.... even the hemi only uses mid range 89.... And will be hindered by 91 octane.... 91 is designed for sports engines... like LS series, SRT-8, Saleen, ect... Octane got a big rip by the ricers who needed to run 91 to handle the performance mod's they put on... ever since then young drivers got the impression that octane somehow increases power...... true it may help a LITTLE.... but it is like adding MAYBE1 or 2 hp.... in the end you will NEVER notice it... any mod you do that add's 15hp or less you will NEVER feel or notice....... anything (like more get-up-and-go)you think you feel is purely a placebo effect... you think it is better because you did something....in reality.... na da

To put it in perspective.... Put a 100lb dumbell weight in the bed.... you think the truck is going to feel more sluggish... take off slower... ect... nope... same goes for adding less then 15 hp... not going to do much... and the sad part is that is 15 hp at the flywheel... not the rubber ones.... same with the 1 or 2 hp.... at the flywheel.... save the money at the pump and don't run 91 unless you are doing real performace upgrades....

 

i always use89 in pretty much everything....cept for my ram i use 91 or higher...i have the Performance 91 tune on my truck so thats why (before that i used 89)...and i also run 87 in my ramharger...but if it breaks i'm not too concerned lol

 

I have always run 91 and probably always will. Some people swear by 87 or 89. The octane is not as important as the place you buy your gas. Buying the cheapest gas you can find is not frequently the best deal, in the long run, especially a generic company. I will look forthe cheapest gas from the stations I trust the most. I really don't mind if filling my tank costs ONE DOLLAR more buying gas for $2.71 a gallon from a station I trust instead of the generic ****ty gas that costs $2.66 a gallon (the cheap gas will definately cost more in the long run).

 

I ran Sunoco 87 octane in my 4.7 for a while but then changed to the 89. I notice a 2 MPG increase after going to the 89 and it seems to run a bit smoother. Maybe its only in my head but its not much more to go with the 89. Just my 2 cents.

 

the octane rating has really nothign to do with power. It more has to do with how hard it is to light that gas on fire. that's why engines that run very high compression and lots of power need to run a higher octane fuel. they make a lot more heat and inside the cylinders is a lot hotter and if you dump in 87 octane that fuel will light before the spark plug goes and well that causes a bit of a problem know what I mean. like if ur car is pinging lotta times it's cuz there's carbon buildup on the cylinders which glows red hot after the combustion cycle and it is what lights the fuel before it's supposed to. a higher octane fuel can remedy this by making the carbon buildup not light it.

 

Will the 87 hurt a hemi motor? The dealer said to run 87 because they gave me a card to fill it up the first time. So, that is all I have ran only had the truck a month. I just read in the manual the other day(and on here) that it calls for 89.

 

I USE 91 WITH THE JET CHIP IT DOES MAKE A DIFFERENCE.WITHOUT THE CHIP 89 IS GOOD,REGULAR IS NO GOOD FOR THE HEMI TRUST ME.

 

The 4.7 should be completely happy with 87. The Hemi will run on 87, but it likes 89 way better. When I bought my '03 a month or so ago, the dealer had been using 87, not knowing any better. He's been fed 89 since then and he's a lot happier now. I don't check regularly, but it seems the mileage has improved. The "butt dino" can feel the difference.