The owner's manual recommends 89.

 

The owners manual also says you can use 87, but they do recommend 89. I use 87 all the time because any of the higher octane contain ethanol here in Iowa. I get about 2 mpg more with the 87 non ethanol that is why I use it. Also the ethanol seems to make O2 sensors life span shorter.

I don't notice any performance difference. When I tow my fifth wheel in the summer on 89 with ethanol I get 8 - 9 mpg at best. With the 87 I have never gotten less then 10.5 mpg. Without the trailer here in the winter I am getting about 12 mpg on 89 and 13.5 on the 87. In the summer I get about 13.5 mpg on 89 and 15.5 mpg with 87. I have tested this many times using two back to back tanks of each fuel for each test.

Unless I see something that states 87 will blow my motor up I will not use that corn juice for anything.

 

As I've stated about 100x in this section, the manual "recommends" 89 but says 87 is "ok". BUT every Hemi engine I've seen have a cylinder or multiple cylinder failures (not including '03 spring related failures) has been from running 87 octane for extended lengths. I've also seen some of the cylinder walls that didn't fail and they were scored to hell from pre-detonation.
It's the long term pre-detonation you don't necessarily hear that causes the most harm, as people will usually address severe knocks & pings they can hear.

An engine with a compression ratio of over 9.2:1 should be using 89 octane fuel exclusively. The 03-08 Hemi is 9.6:1...



That's a tough call, as I stated I've seen a LOT of long term negative effects of running 87, but I HATE ethanol as well. For years I went out of my way to buy gas at non-ethenol stations but currently I now only have one in my area, 12 miles away and what really makes it a PIA is the small independent doesn't do credit cards, so I have to pre-think when I'm gonna need gas and hit the bank or ATM for enough cash. What really sucks is the closest branch of my bank is 11 miles from my home IN THE OPPOSITE DIRECTION! So now I just go wherever, get 93 octane (as my tune dictates I need) and I treat EVERY tank of gas with Star Tron, which eliminates ethanol. Like you, I see 1.5-2 mpg better with ethanol free gas, but get about the same results with the Star Tron...

 

May have been said 100 times, but this is the first time I've heard it. Hard to believe as much as I troll here, but typically my luck. Thanks for clarifying it though. So, has the damage been done to mine at 92k miles or is it not too late to switch?

Funny, Evan runs 87 because it's all he can get without ethanol. Where I live, you can only buy ethanol free in Premium-91 and there is but 1 station within 30 miles that sells it - and they are out of it half the time.

 

so i see you all saying no to ethanol, ok i get that but what about it being used in Flex fuel systems? (not talking E85, i hate E85 makes my truck sound like a rice rocket) but like 91 with 10% ethanol? vs pure 91, in the flex fuel systems.

 

Greg: You've probably got some scoring of the cylinder walls, but switching to 89 now will prevent any further damage. If there is no apparent problem now, you're probably ok, but if you run a tad low on oil between changes, it's a sure indication that you've lost that tight piston seal and probably a tad of compression. I'm not throwing up a red flag here, I know guys with Hemi engines with 180k miles on them who've only run 87 octane, BUT when one does blow an engine it always seems to be someone who either admits to running 87 or there is unmistakable evidence of pre-detonation you would only get running 87. I just think the odds of having a cylinder or multiple cylinder failures increases dramatically with the lower grade fuel. At $3-$4 per fill up I just think it's a no brainer to run the 89 octane as opposed to taking a chance on a blown engine at some point down the road.

Oh, and yeah, the only place left around here that sells non-ethanol only offers it in 93 octane, their 87 & 89 is E10.


Cowboy: Flex fuel vehicles use special seals and lines that are impervious to alcohol (ethanol) eroding. Even newer ('07 and newer) vehicles not rated for flex fuel have components that are more resistant to ethanol than older vehicles. You ever notice that on your lawn equipment the primer bulbs and fuel lines get eaten away when 10 years ago they'd last the life of the tool? No, it isn't because of cheaper, Chinese made parts, it's the ethanol eating away the plastic. Rubber seals have the same problem. That's why I use a product that removes the ethanol on all my yard equipment (and vehicles).

However, fuel economy will be better with no ethanol. People with flex-fuel system often report as much as a 25-30% loss of fuel economy when running E85 which negates the cheaper price. I get about 2 mpg better on both of my vehicles when running ethanol free fuel or treating ethanol fuel with Star Tron Stabilizer...

 

Gotcha Hammer. The only time I experienced unexplained oil loss is after going to change my first batch of synthetic oil. I've changed it twice since then and there was no significant oil loss. The first time, I didn't over run my mileage interval but did go well past the time interval. In other words, over a lengthy period of time, I didn't drive many miles and the miles I did drive were short, city trips.

I'm with you on the price difference. If I'm paying $75 a fillup, what's a few more dollars for 89 octane. I would have always taken that approach but I didn't realize I needed 89. Truck always ran fine on 87.

So, would you say it's not so much an issue with ethanol, though there are issues there otherwise, it's more the octane? Forget the 30 mile radius, I don't know of a station anywhere that sells ethanol free gas in less then 91 octane. And like I said, the closest station is out of it often. No more miles than I drive, I'll probably start using an ethanol additive and switch to buying 89 from here on out.

 

Pick up a bottle of Star Tron (most stores with a marine fluid department has it - it's about $8 for a bottle that treats 128 gallons of gas at Wally World). Follow the instructions (first tank - 1 oz. per 8 gallons, after that 1 oz. per 16 gallons) and see if by the end of the 3rd tankful you aren't seeing a 1.5-2 MPG increase. Most also comment that the engine idles and runs a little smoother too.

At even 1.5 MPG better, it WAY more than pays for the $8 bottle that is essentially good for five complete fill-ups...

 

Will do Hammer. Is that stuff any better or same as the stuff that stabil advertises? Or is the stabil stuff not even for motor vehicles? Maybe it's just more expensive? I haven't priced it. I know by brother uses it in his boat when he has trouble finding ethanol free gas.

 

I used to use Sta-bil in every bass boat I ever had and all of my seldom-used gas engines. But traditional Sta-bil is only a fuel stabilizer. Does nothing for the breaking down of plastic/rubber in the fuel line and clogging of carbs that ethonal causes. I still was replacing primer bulbs yearly, which I haven't had to do in the three years I've been using Star Tron in my yard equipment gas.
Star Tron (which by the way, is made by Star Brite who has been making marine engine products since before I was born), is a stabilizer, a re-conditioner and prevents phase separation which is basically what ethanol does to gas.

I believe Sta-bil has recently come out with an ethanol formula as well. Dunno if it does all that Star Tron does or not - but again, traditional Sta-bil does nothing about ethanol...