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So if only 87 or 91 are available at the station, which should I choose?
I have been using the 91.
 
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So if only 87 or 91 are available at the station, which should I choose?
I have been using the 91.
If you are at an altitude of more than 4,000 feet the 87 will give the same performance that 89 normally would (at this altitude). If you are at sea level it's a tougher call, the 91 is more than you need but the ECU will dial the engine timing back a bit on the 87. Find a different gas station.
 
I have the exact same issue (question) as the original poster. I live in Denver, bought a 2011 Overland with the Hemi engine and purchase fuel at Costco, where only 87 and 91 octane are available. The 91 octane at Costco is usually priced the same or lower than 89 at "regular" gas stations, so if there are no issues with using it with the Hemi (even if there is no benefit) from a purely economical perspective it makes sense....

Just my $.02
 
OP most likely still had some regular gas in his tank and when filled up with premium ended up with a mid grade blend.

If it ran better that way, then it is a strong indication that he might consider running mid grade from now on as recomended in his owners manual and fuel filler sticker.

If always buying from Costco, consider switching back and forth between regular and premium to optimize costs. (Filling up around 1/2 tank each time).

If you run the cheaper gas, the computer will pull timing to stop any knock. This will reduce fuel economy and torque. Some might not notice it, but it will happen.

Jeep has designed this car to be able to run on regular, without damage, in a pinch if mid-grade is unavailable, but to perform at it's best with mid grade in the tank.
 
OP most likely still had some regular gas in his tank and when filled up with premium ended up with a mid grade blend.

If it ran better that way, then it is a strong indication that he might consider running mid grade from now on as recomended in his owners manual and fuel filler sticker.

If always buying from Costco, consider switching back and forth between regular and premium to optimize costs. (Filling up around 1/2 tank each time).

If you run the cheaper gas, the computer will pull timing to stop any knock. This will reduce fuel economy and torque. Some might not notice it, but it will happen.

Jeep has designed this car to be able to run on regular, without damage, in a pinch if mid-grade is unavailable, but to perform at it's best with mid grade in the tank.
This debate never dies. You can run 87 ALL THE TIME without issue. You don't need to feel as if you can run it in a "pinch" and otherwise need to run 89. The vehicle runs fine on 87. I have a HEMI in my 2009 Dodge Ram Laramie and I EXCLUSIVELY used 87 with NO problems and have over 51K on the odometer. If you want to run 89 to optimize the performance, go ahead but if you want to save money use 87. There's ZERO reason to be concerned with using 87. Not trying to pick you on Uncle Paul but I want to make sure we aren't needless scaring people into believe using 87 will in some way harm their vehicle. I have NEVER noticed ANY knocking whatsoever in my HEMI on my Ram and not in my HEMI on my Jeep after one tank either. I'm speaking from experience here.
 
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I used 87 in my 08 JGC Limited with the Hemi, I never used anything other then 87 for the three years I owned it, and never had and an issue.
 
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Always use what is recommend for performance and computer requirements. Even with premium it's only a couple of dollars more. I pinch pennies but never with my vehicles.
 
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IMHO, you are better off worrying about the overall quality of the fuel you use. 87 Mobil, Chevron, etc.. would be preferable to say, ARCO 91. Really what I think it comes down to is benzene vs. Ethanol content. The lefties want more ethanol and less of the "carcinogenic type" components in gasoline. I live in CA currently, and can tell you that any brand or octane of gasoline is garbage here compared to my home state of CO. Why? Because of CARB, EPA and the lefties. WA state just adopted the CA laws and their gas is weak now too. I can smell the difference. Benzene is what gives gas that heavy, sweet aromatic smell. Ethanol, in a word, just smells "bad". It kind of reminds of grease. Ethanol and benzene accomplish basically the same task of limiting predetonation. Ethanol is corrosive and bad for fuel system components and also causes gas to go "stale" a lot faster. Benzene is pretty much awesome but its bad for humans and extremely carcinogenic. The lefties have made your choice for you on what you buy. Standby all other states for the same crap gas and donkey dick "vapor recovery" pump handles we have in CA. CA residents you know what I mean if you ever have filled a motorcycle in CA. Lame. Sorry for my rant. CA sucks. It should be given to Mexico in Exchange for sealed borders. My .02.
 
I use 87 in my 2011 with just over 9k miles. Never had a single issue and it runs great all the time. I never compared gas milage so can't comment on that.
 
I was very low on gas and late for an appointment the other week. I had an old 5 gallon gas can with 50:1 premix (which was probably a year old and only 87 octane) from my dirtbike. I threw that in and then filled up later that day. I do love the smell of premix. :)

I usually put 89 octane in anymore. My wife still puts 87 in it when she fills it up.

I really don't think it matters either way. As long at whatever you put in still burns, you're golden. :)
 
hi all jeepies . here in Australia we have 4 different octanes of petrol which are 91 e10 ( ethanol ) 91 octane 95 octane and 98 octane . for the first 6 months of owning my jeep 2014 5.7 v8 overland I ran 98 octane with no deteramental effects except a very noticeable increase in performance and fuel ec0nomy when compared to 91 octane which I am running now which leaves it running like a tired snail ( comparatively ) . if I am not having any issues with knocking or other problems would it be ok to use it ?
 
hi all jeepies . here in Australia we have 4 different octanes of petrol which are 91 e10 ( ethanol ) 91 octane 95 octane and 98 octane . for the first 6 months of owning my jeep 2014 5.7 v8 overland I ran 98 octane with no deteramental effects except a very noticeable increase in performance and fuel ec0nomy when compared to 91 octane which I am running now which leaves it running like a tired snail ( comparatively ) . if I am not having any issues with knocking or other problems would it be ok to use it ?
If I remember correctly, you folks down under use RON ratings for fuels. The best power (and thereby economy) you can get out of any engine is by running the lowest octane the engine will handle without preigniting the charge. Food alcohol (ethanol) contains less energy than gasoline by volume. About 40% less I believe. However, ethanol is about 110 octane so it does increase the RON. Even so, I would choose alcohol free fuel any day of the week. Being in your shoes, I would run the 91 E0 all day long. Your economy will come up and so will the power as soon as the ECM learns the timing and ignition.
As a back story: I used to believe that you had to run the octane recommended for best performance. It is a lie. The higher recommended ratings are for emissions purposes only. Since getting into the performance motorcycle world years ago, I have found this out. We can consistently get 2 more horsepower by simply running 87 AKI instead of 93 AKI (that is US has grades) as the manufacturer recommends. Fiddling with the tuning can net more. Even with tuning, the lower AKI will produce more power. These are engines operating at 13:1 compression. Much more sophisticated than a pushrod Hemi is.
 
Evil', in the US, Jeep "recommends" 89 octane (mid-grade) for best performance, not 91/93. But as I've noted in previous threads, I've only ever run 87 for all but one half tank over 106K miles with no disappointment. If I were doing heavy towing or had a lead foot, I'd use the 89 for sure, however.

I do agree about avoiding the Ethanol-based stuff with more than 10% for the V8 as it's not (at least in North America) setup for flex fuel like the V6 is.
 
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I like to keep things simple and it looks like the conclusions we can draw for the 5.7L engine are:

1. The manual recommends 89 octane.
2. Many people here run 87 octane without any apparent problems.
3. If you live at higher altitude, like Denver, the 87 octane may be the essential equivalent of 89 octane at sea level.
4. Running 91 or 93 octane doesn't add any value.
5. Ethanol is bad because it corrosive and Benzene is bad because it's carcinogenic, so pick your poison.

Bottomline for me is I will run 89 octane from a reputable gas company as long as it's available, if not I'll run 87 octane. I'll run premium if nothing else is available. Tell me if I've gotten something wrong.
 
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I follow using 87 octane for 99% of my driving, any towing or extreme mountainous driving I use 89.

I remember buying this V8 GC 6 years ago and people telling me how I was going to spend all this money on gas with a V8 lol. Gas has done nothing but go down in price since then, filled up at Costco(top tier gas) for $1.87 last time. Gas bill is definitely my cheapest bill every month, now if I could just get my cable bill as cheap as my gas bill is every month lol
 
I like to keep things simple and it looks like the conclusions we can draw for the 5.7L engine are:

1. The manual recommends 89 octane.
2. Many people here run 87 octane without any apparent problems.
3. If you live at higher altitude, like Denver, the 87 octane may be the essential equivalent of 89 octane at sea level.
4. Running 91 or 93 octane doesn't add any value.
5. Ethanol is bad because it corrosive and Benzene is bad because it's carcinogenic, so pick your poison.

Bottomline for me is I will run 89 octane from a reputable gas company as long as it's available, if not I'll run 87 octane. I'll run premium if nothing else is available. Tell me if I've gotten something wrong.
I've run several tanks of each and my seat of the pants, along with some readouts from Torque program ODB gizmo, is that when you use 87 you definitely get reduced power (I'd guess a 20 hp loss) and the engine power production isn't as smooth as it is with 89. As the computer adjusts to compensate for the lower octane the power it produces kind of goes up and down when accelerating. Sometimes I can feel it cut back on power during acceleration with 87. Running 91 I could feel no difference than running 89. So most of the time I use 89 as I did not like the reduced smoothness of the power output with 87. If I was going to go on a long trip driving mostly at steady speeds and not towing I might use 87 to save a little on gas.
I tried to get an idea of changes in gas mileage but couldn't pin it down enough to say with any degree of certainty if there was a difference. It sort of seemed like 89 gave better gas mileage but if it did it was no more than 1 mpg.
 
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