Jeep Garage  - Jeep Forum banner

Fuel Requirement GC 2014 V8 owners

8K views 36 replies 18 participants last post by  Jim_in_PA 
#1 · (Edited)
Any of you are using unleaded regular 87 octane on the V8?

Or should I use only 89 octane?

I know that the spec says it is acceptable 87 and 89 is recommended ... but what are the implications ???

Thanks:thumbsup:
 
#2 ·
Slightly less hp are the implications. The vehicle is smart enough to sense that it has 87 in it, and will pulling timing back to compensate. This yields a slight (15ish?) loss in hp.

People will tell you that its better to use 89 long term for a variety of (mostly bogus) reasons. Keep in mind, the Hemi is also a work truck engine, and can run for hundreds of thousands of miles on 87.

Sometimes I feel like I get slightly better fuel economy using 89. It may be a psychological thing though.
 
#19 ·
I dont think it is psychological. Compression Ratio has a huge impact on the otto efficiency of an engine. The compression ration doesnt change, but the advance of the spark is effectively a dynamic change to compression ratio and hence increases efficiency... Efficiency is a double edged sword in that more power normally makes the right foot put more of a grin on your dial... but that efficiency (all things being equal) will also give better economy. The knock sensors will advance the ignition in a vehicle like this and you will see economy increases... We get 91 standard octane, 95 and 98 octane in Oz. You do measure Octane via RON, dont you in the US?
 
#3 ·
While I'm driving a MY12, the specifications are the same. I run 87. The place I buy most of my gas (Costco) doesn't even sell 89. I've not had any performance issues and get good fuel economy.
 
#6 ·
I definitely do get better mpg's with 89, between 1 and 2 more mpg's when using 89. I only do Shell and at least here in southeast Ontario 87 has up to 10% ethanol, 89 up to 5% ethanol, and 91 0% ethanol. I guess the difference has to do with the ethanol %.
 
#7 ·
That makes sense, nvfusa...Ethanol unfortunately lowers fuel economy. I don't know what the blend is around here as the pumps just have stickers that say "up to 10% Ethanol" on them.
 
#8 ·
I bought gas for my Jeep for the first time today. I was happy buying 89 for my Hemi, coming from a vehicle that needed 93.

Using 87 won't hurt anything, but the computer will retard the timing to prevent pinging. This will reduce performance and mileage. Whether it's a noticeable amount is any body's guess.
 
#13 · (Edited)
maybe on your fusion it is not working, as it has a rubbish engine inside :)

but modern engines check automatically what kind of octane they get and know
how to handle.

and the v8 hemi is the same engine running in the usa and in europe.
here it is recommended to use them with 95 or 98 octane
and it will definetely need more gas when running with only 87 octane.

even nearly ALL high performance cars need to use 98 to 100 octance gas,
what do you think why ?!? ... as only with this gas the engines can get the
maximum power out of it.

and this is much better gas then to go with only 87.

it is like that. !!!
 
#14 ·
I believe step one is the fact you are in Europe. If I remember right you guys measure octane different over there.

High performance cars do require higher octane gas because they are designed for it, not to insult anyone here but the 5.7 hemi is by no means a high performance engine. It will not take advantage of the higher octane. It doesn't sense what octane you have in the tank it will just run as much advance as is in the timing map until it detects detonation, then it will start pulling timing until it goes away, then start adding timing until detonation starts again and keeps going back and forth until it finds where the detonation is and runs the timing there. If you add some sort of programmer then sure if you have the 91 or 93 octane tune you should be running that, if not you are just throwing money away. For the record it wasn't just my fusion I have done this to, every vehicle I have owned I try it, same thing every time.
 
#15 ·
maybe we do measure it different .... but that huge difference. ?!?
... but thanks for the information, good to know.

but quite poor for an engine built in 2013 ... not having these standard features on board.

would be more easy if there would be one world standard at all :)
 
#16 ·
You do, and it is quite different.

Running high test in a Hemi will do you no good, it's calibrated for 87/89. If you use 89 it ill run at normal timing and prove slightly more power. If you run 87 it will pull timing and slightly reduce power. If you run 91 you will only get the effect that the 89 had, and it may interfere with the MDS system (based on reports on the boars here, not sure how accurate that is so take it with a grain of salt).

We still have to get a lot of Europe to drive on the right side of the road before we even think about measuring octane the same way.
 
#20 ·
Readin further on here... If the overseas versions do not advance to the point that they will take advantage of higher octanes (RON ratings) then you wont see the advantages... Makes me think that a tune in Aust will make a huge difference to the output figures if I run 98 Octane.

Why is it that America runs all its measurements different to the rest of the planet? You guys do realise that there are a lot more people on this planet that do agree to a "Standard International" (SI) setof units... Even the Poms cant agree though, they have their own Gallon... LOL! At least we speak the same language... mainly!
 
#23 ·
I've had a 2005 "C", a 2005 GC and now a 2012 Ram all with the Hemi. I never have used the 89 in any one of them and I have no complaints whatsoever relating to performance. It used to be that 89 was only 10 cents more than 87. Now most stations around me have a 20-30 cent difference, so over time running the 89 would cost quite a bit more with no great advantage.
 
#25 ·
If you fill your tank with half 87 octane and half 91 octane (as stated above Buyer's Clubs only sell these octanes) does it become 91? Anyone educated in this field know or does common sense have nothing to due with petrol chemistry. I'd like to know for my Ram Power Wagon also.
 
#28 ·
I was lazy. As usual a few minutes research on the web finds numerous petrol-engineers, racing teams and even fuel distributors saying it is as simple as mixing. They say the 89 octane tanks at gas stations simply mix 50/50. There are even octane mixing calculators online.
 
#30 ·
Does the switchover from 87 to 89 usually take a tank or so to see the benefits? Reason I ask is I was getting good gas mileage on 87 but decided to try out 89. So far on this first tank of 89 I am noticing a drop of around 1.5mpg compared to what I was getting before - not sure if the "timing corrections" take a bit to get worked out?
 
#31 ·
There's no switchover that happens. The engine detects knock, and if excessive knock is present, then the computer will pull timing. 89 octane is less prone to knocking than lower octane. Your drop could be that there is more ethanol in the 89 octane.
 
#32 ·
Does anyone here own a 2014 JGC? I have the Summit with the V8 and I just did its first fuel fill yesterday. I had a heck of a time trying to get the gas nozzle at the station to go into the Capless fuel thing. I eventually got it in but took me a long time. I checked the manual and it dosn't really say much about fueling. I'm just wondering if my capless fuel system is functioning properly. It was really a hard time to try and get the fuel nozzle into the tank.

I have a service appointment at the dealer on Thurs. I forgot to mention it when I booked the appointment but will ask when I drop off the Jeep.

I'm bringing in my new 2014 Jeep in for shaky steering wheel at high speed at 110-120km/h. My brother seems to think it could be the weights aren't balanced properly on the wheels. Also I have condensation on my headlights that goes away after a few minutes. The lady on the phone for service said there was a bulletin about that but they won't do anything unless the condensation dosn't go away after a few mintues. Mine goes away but I'm wondering if this could be a problem down the road or in winter time from freezing etc.
 
#37 ·
I've sometimes had "sensitive" nozzles with the non-cap-less fill of my vehicles over the years! Usually can get around it with a little wiggling, but...not always...
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top