I have noticed on average a 1.5mpg gain by running the SC 91 tune w/91 octane. Depending upon the price difference it may be to your benefit to run premium and the premium tune...

 

wow...i can't believe i have been running 87. i never really knew the difference between the octane levels (and still don't) but today i went with 89. i was nervous at first bc i have never used 89 in any of my vehicles. not sure if i'll notice anything different but a 3 dollar difference is better than thousands down the road.

my wife has a 03 mitsu outlander with 150000 miles on it, should we switch to 89 for her too? if this is the case, then every vehicle i own down the road should be on mid grade....btw my truck is stock. i'm glad i found this thread to put my mind at ease. but $75 is not that fun to see drained just on damn gas..oh well love my ram!

 

The Mitsubishi DOHC 4G6 series engines have a compression of about 7.8:1 and are tuned to run on 87 octane gas. There is no benefit to running any higher octane fuel.

Also, you have a 4.7L V8 with a compression ratio a bit lower than that of a Hemi, plus it's de-tuned a good bit more from the factory, there is no reason you need to run 89 unless you hear pre-detonation. 89 wouldn't be a bad idea when towing/hauling or if you live and drive in a region with some pretty good size hills to have to pull.

The internal engine failures I speak of are specifically in Hemi engines which get a steady diet of 87 octane fuel...

 

If you don't have a tuner, you will be quite safe running 89 octane. There is no real benefit of running the 93 on a stock tune.

 

^^^^^^^^^^^^^^^^
What he said. Dodge says 93 is not recommended.

 

So dodge syas dont run 93 and run 87 but people on here suggest run 89? Im going to go with the people on here. Running an 03 hemi with an exhaust and a CAI should I run the 89 or upgrade to the 91/93? Also anyone use those JET Performance Modules?

 

Dodge doesn't say DON'T run 93 and Dodge doesn't say RUN 87.

Dodge says RUN 89 for optimal performance but 87 is acceptable with some degradation in performance. Dodge says you will see NO benefit from running 91 or 93 over 89.

MOST of us only really disagree with Dodge on the 87 being acceptable part, because there have been a wide number of reported engine failures from people who only run 87 octane fuel.

As for the Jet Chip, it was popular when it first came out, but after guys started running dynos with the chip and seeing VERY minimal gains usually coupled with a DECREASE in fuel economy it lost popularity FAST.

Do a Superchips or Diablo or even an SCT if you are into in-depth mods and require a custom tune. Most others on the market range from a total rip-off to only offering a fraction of the advantages seen with those three tuners...

 

Jet is not worth their price. The manuals say to run 89 but 87 can be used. Again, if you do though, you are subject to things internally in the engine that you cannot see or hear without data loggers to monitor certain parameters of the truck like "knock".

The 93 not to run 93 because the engine isnt tuned for it. My engine is custom tuned and my timing is setup for 93 so thats what I use. It gets more power than 87

 

Ok ill run 89 than. But as far as the jet. Id spend th extra money and get a superchips or other programmer but i dont know the first thing as to what I am doing with it. (This is also in another thread too sorry Hammer) I want to lear the programmers and stuf I just dont know where or what to look at.

 

if somehow the extra 10c per gallon for 89 would bankrupt anyone they have obviously not been responsible with their finances.

I run whatever premium is at the station i'm at. ranges between 91-93. I doubt it gets better performance than 89 but for the slight increase in price it's not going to hurt anything. Just further helps to prevent any knock or ping