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Old 11-21-2012, 09:20 AM   #1
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4.0 Picky about gas?

Thanks for reading.

I know the 4.0 is picky about spark plugs...

I usually use Shell or Exxon gas stations

About 3 months ago I had engine light P2096 code come up after fueling up at a Valero... Jeep runs fine but I ran the Jeep until E then refilled with Shell and resetted the engine light... Never came back on after 1K miles so it must of been the gas I'm thinking...

Last night I was stuck in traffic on E w/ the light on (must add this is scary lol)

I saw a Valero and I'm not a fan of them but had no choice and filled up halfway.

Well this morning on my way to work the engine light P2096 came back on while on the highway...

Seem like my Jeep doesn't like Valero's gas.

Any other 4.0 owners know anything about this??

Any suggestions are appreciated.

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Old 11-21-2012, 09:26 AM   #2
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yup.. mine is picky as well.

So was my 93 Grand Cherokee. They both got better mileage and ran better on shell and BP.
I assumed it was water levels in the gas, and even went to one of the gas stations that made mine run horrible to politely let them know. They actually tested it in front of me and showed me they were good. So either they were full of it and trying to please me, or its something else.

:shrug:

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Old 11-21-2012, 09:28 AM   #3
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I have yet to have an engine light come on because of it but I have clocked the MPG with a few different stations and noticed that the mileage goes down about 2 MPG with certain fuel stations. I did it numerous times to average it out. I have not tried the Valero station yet. But I will say my motor definitely likes certain fuel so I can see it being possible.
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Old 11-21-2012, 09:35 AM   #4
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my 4.0L gets whatever 85/87 octane crap is cheapest. it hasn't complained yet.
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Old 11-21-2012, 09:36 AM   #5
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Wheaties is my third vehicle to love shell. (hes my current 97 TJ)
Penny was always grumpy on anything other than shell 87 (she was a '83 Porsche 944)
Cheerio would deal but always ran considerably smoother on shell (he was a '93 ZJ)
- cheerio ran so smooth in fact you could balance a beer on the intake while working on it, without fear of it falling off or getting shook up. (yes even while starting and running)
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Old 11-21-2012, 09:41 AM   #6
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P2096

exhaust leak
engine mechanical fault
02 sensor fault
fuel contamination

Has to be the fuel with my Jeep I only have 61K miles on it and the timing of when the light comes on is pretty obvious.
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Old 11-21-2012, 09:42 AM   #7
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My new 4.0 goes in next week. Can't wait!
Hopefully she won't be picky on what I give her to drink.
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Old 11-21-2012, 10:06 AM   #8
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my 4.0L gets whatever 85/87 octane crap is cheapest. it hasn't complained yet.
So the saying everyone's Jeep is different applies to gas also it seems?

I hope its nothing else I don't feel like dealing with a dealer...
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Old 11-21-2012, 10:46 AM   #9
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Toss in some Lucas full system cleaner, and avoid Valero.
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Old 11-21-2012, 11:06 AM   #10
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Where I live valero has super tuesdays where you can get 89 for the price of 87, I was on that kick for a while but have figured out that my jeep loves the shell gas after having the jeep for about a year. I have two part time jobs and school so Im constantly starting the jeep probably4-5 times a day. I just prefer shell I seem to get about +2mpg over valero. dont use exxon its always more exspensive plus kroger has deal with shell.
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Old 11-21-2012, 11:37 AM   #11
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My 4.0 is fairly picky as well. I used to fill up at the cheapest places I could find (Arco,Valero, Etc). I found got around 2-3 mpgs less filling up with those brands. Now I only use top tier gasoline (76, Chrevron, Shell) and my mpgs went back up to where they were supposed to be. I did the math a while ago and found it was cheaper in the long run to get the more expensive gas.
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Old 11-21-2012, 11:48 AM   #12
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Quote:
Originally Posted by UnlimitedLJ04 View Post
my 4.0L gets whatever 85/87 octane crap is cheapest. it hasn't complained yet.
x2 on the 87 with all 3 of ours
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Old 11-21-2012, 12:19 PM   #13
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Originally Posted by spenserb View Post
Where I live valero has super tuesdays where you can get 89 for the price of 87, I was on that kick for a while but have figured out that my jeep loves the shell gas after having the jeep for about a year. I have two part time jobs and school so Im constantly starting the jeep probably4-5 times a day. I just prefer shell I seem to get about +2mpg over valero. dont use exxon its always more exspensive plus kroger has deal with shell.
Just a note, putting in 89 has zero benefit. If fact higher octane is harder to ignite and could burn a little more incomplete.
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Old 11-21-2012, 12:29 PM   #14
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Just a note, putting in 89 has zero benefit. If fact higher octane is harder to ignite and could burn a little more incomplete.
The Jeep will burn 89, but it will make less power than 87.
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Old 11-21-2012, 01:25 PM   #15
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I just put in some fuel system cleaner and filled it up. Should I reset the light or should it go off on its own?
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Old 11-21-2012, 01:33 PM   #16
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Octane level does not determine power output of the engine. Octane level is a measurement of the fuel's resistance to ignition. In high compression, forced indiction, nitrous etc. the fuel has a greater potential for preignition of detonation which you do not want.

Yes it could make less power if you do not have complete combustion. It could also leave deposits. For practical purposes in this application, it is not going to make less power. 89 is not going to make any more. People get the misconception that usung high octane will make more power.
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Old 11-21-2012, 01:37 PM   #17
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I just put in some fuel system cleaner and filled it up. Should I reset the light or should it go off on its own?
You mean the check engine light? If the problem is cleared, it will go out but fuel system cleaner should not have set a CEL. Get the code. If you have a 00+ turn the key off-on-off-on-off-on and the code wil appear in the odometer.
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Old 11-21-2012, 02:21 PM   #18
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People get the misconception that usung high octane will make more power.
Using a lower octane than required can result in less power, that's for certain. It's all a question of whether it's "excess" octane.

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Octane level does not determine power output of the engine.
It all depends on which side of the equation the "greater than" sign points to.
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Old 11-21-2012, 02:30 PM   #19
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For practical purposes in this application, it is not going to make less power.
Practical purposes...true that a person may not notice while driving. But it would show "less" on a dyno if the engine was optimized (complete burn) for 87.
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Old 11-21-2012, 02:35 PM   #20
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Using a lower octane than required can result in less power, that's for certain.
In that scenario, more power is created...but it's creating much more heat and detonation since the flashpoint is lower (easier to ignite than optimal for engine). So often pistons melt down can occur.
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Old 11-21-2012, 02:39 PM   #21
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I am surprised to hear that some of your Wranglers are finicky about their gasoline. None of mine have ever been--not remotely. Indeed, I'm pretty certain the 4.0L could run on dirty pond water, in a pinch.
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Old 11-21-2012, 02:39 PM   #22
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In that scenario, more power is created...but it's creating much more heat and detonation since the flashpoint is lower (easier to ignite than optimal for engine). So often pistons melt down can occur.
Heat and power are not the same thing. Would you like to explain how detonation occuring way early in the compression stroke creates more power. Or how engines with antiknock sensors that retard the timing when detonation occurs create more power?
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Old 11-21-2012, 02:39 PM   #23
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You mean the check engine light? If the problem is cleared, it will go out but fuel system cleaner should not have set a CEL. Get the code. If you have a 00+ turn the key off-on-off-on-off-on and the code wil appear in the odometer.
P2096 came on about 10 miles after fueling up at a Valero gas station.

o2 sensor or fuel contamination is what it means.

few others on the list but I don't have a leak in my system my Jeep runs smooth.
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Old 11-21-2012, 02:42 PM   #24
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I am surprised to hear that some of your Wranglers are finicky about their gasoline. None of mine have ever been--not remotely. Indeed, I'm pretty certain the 4.0L could run on dirty pond water, in a pinch.
Satisfying the engine is one thing. Keeping the emmisions system happy is a substantially different thing. Note that the OP reported no problem with his engine.
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Old 11-21-2012, 02:46 PM   #25
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Heat and power are not the same thing. Would you like to explain how detonation occuring way early in the compression stroke creates more power. Or how engines with antiknock sensors that retard the timing when detonation occurs create more power?
I agree they are not the same thing...the heat is the result of the pre-fire. The power comes from the low octane fuel.
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Old 11-21-2012, 02:50 PM   #26
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The power comes from the low octane fuel.
What comes from excessively low octane fuel is detonation. Detonation does not contribute to power in a positive way.
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Old 11-21-2012, 02:58 PM   #27
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What comes from excessively low octane fuel is detonation. Detonation does not contribute to power in a positive way.
Depends on the motor. If such a fuel existed to have 40 octane rating and a motor was built for it...it would not detonate. "Low" is simply relative to the specific motor.
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Old 11-21-2012, 03:01 PM   #28
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Depends on the motor. If such a fuel existed to have 40 octane rating and a motor was built for it...it would not detonate. "Low" is simply relative to the specific motor.
If it doesn't detonate, it would be hard to agrue that the octane was excessively low.

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What comes from excessively low octane fuel is detonation.
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Old 11-21-2012, 03:09 PM   #29
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I keep to the big gas station chains and my Jeep is happy. They have a station called "Maverick" where I live and my Jeep kept stalling when I filled up there once. Never again. I would rather pay a couple cents more and know it is good gas.
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Old 11-21-2012, 03:46 PM   #30
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an ole wise engine builder recently told me that high octane gas is only needed by high compression engines.

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