unleaded or super

[cm2005300]

do you guys use unleaded or super any diffrence??

[CANDYAPPLE]

3.5's call for 89 octane. They will run on 87, and the computer will adjust, but you will not get the best mileage or engine wear. I have driven my 3.5 on 89 since new. My father bought a used 2006 300 Touring which was a former rental. It probably only used 87 octane, and that's what he has been using. O.K. for his needs, but it is not as quick as my car (With a lot of WOT runs!!)



Cheers CANDYAPPLE

[cm2005300]

So I Ahve The 2.7 Should I Go With 89 Or 91?

[jmckenzie]

I don't think you'd get any benefit from using premium, the manual says that it can cause worse performance than 87 or 89

[cm2005300]

So Maybe Ill Try 89 Then

[magnumdude]

89 on my R/T, as the book says

[NorthVanMag]

The 2.7 does not need 89, you are wasting your hard earned $!

[ZMagnum]

Mid-grade. 89.

[PowerWagon896]

I don't think you'd get any benefit from using premium, the manual says that it can cause worse performance than 87 or 89

All octane does is raise the flash temperature to prevent detonation in high compression engines or engines that have the spark timing or A/F ratios tweaked to the max.

If the engine does not require the higher octane it can indeed hinder performance.

Save your money, run the 87 octane fuel.

Now the "Mango Express"? That is a high compression enginne & yes the spark timeing is twaeked to the max. 93 octane for it.

[cm2005300]

gotcha

[MagNite]

I had a 2.7 in my Intrepid.... always used 87 octane. If that is what your manual says, that is what yoiu should use. You won't get better performance using a higher octane. You have to understand what octane is all about and why engines have different requirements..... here is my understanding... anyone correct me if I'm wrong.

The octane is like a previous poster said... a flashpoint. As the cylinder in the engine reaches top dead center, that is when the spark plug fires and ignites the fuel/air mixture. Now, a higher compression engine is going to have a hotter fuel/air mixture and cylinder temperature than a lower compression engine because the fuel and air is being compressed more. So this is why a higher compression engine needs higher octane, so the flashpoint is higher, other wise using a lower octane could lead to premature detonation in a high compression engine before the cylinder reaches its top dead center, which would lead to power loss. Makes sense to me. That's why it would actually be worse to use high octane in a lower compression engine (the fuel/air would be igniting too late....after the cylinder reached its TDC and was on it's way down. ) and low octane in a high compression engine (the fuel/air would ignite too early... before it reached it's TDC ) . Now todays cars' computers can adjust the timing somewhat in response to the octane, but still, better to use what is recommended in the manual. Whew! Hope that made sense.

[Fred]

[cm2005300]

yea so i started using 89 and the rough idle went away thats why i was thinking 89 but thanks for the help

ps 89 helps rough idle in 2.7's sorry to inform you guys but i guess 89 does make a diffrence

[SlammedSXT]

I have always used premium in all my carsd after 2 months. I run regular to find out mileage and then switch to 91 for better mileage. I average about 100-150 more km on 91 octane. O don't really care about performance, it's all about the pride to ride low and slow!!