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FCA clarification on 2.0L & 91 octane

rommel102

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This is understandable. In winter the Turbo is getting plenty of cold air and is very efficient. In hot weather the Turbo will be less efficient and the engine has to work harder. Adding the higher octane fuel probably counteracts some of the power loss from the hotter air in the intake.

Anecdotally I have tried both regular and premium and have seen zero difference in fuel mileage or performance so far this winter.
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Crusifix

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I'm no expert but I thought that the jury had come back on Ethanol and it was no bueno for engines over the long run.
I missed that verdict. I had been running E85 in my Mustang for three years making loads of power and had no issues. The problem is with older systems that utilize rubber or plastic fuel lines. Any modern vehicle has steel lines due to all fuel in the USA having at least 10% Ethanol in it. E51 or greater is basically 105 octane and will burn cooler and is easier on the engine. The drawback is that you get much worse fuel mileage. It actually burns really clean. I noticed on my Evo X and my mustang that when I ran 93 octane, my tailpipes would get sooty. With E85 they stayed extremely clean.
 

rommel102

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I missed that verdict. I had been running E85 in my Mustang for three years making loads of power and had no issues. The problem is with older systems that utilize rubber or plastic fuel lines. Any modern vehicle has steel lines due to all fuel in the USA having at least 10% Ethanol in it. E51 or greater is basically 105 octane and will burn cooler and is easier on the engine. The drawback is that you get much worse fuel mileage. It actually burns really clean. I noticed on my Evo X and my mustang that when I ran 93 octane, my tailpipes would get sooty. With E85 they stayed extremely clean.
Unless Jeep tells me to start putting E85 in the hurricane I'll stick to regular old fuel that is only subsidizing the corn industry at 10% or less :)

I think that recent corn news has me soured to it all :)
 

Crusifix

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This is understandable. In winter the Turbo is getting plenty of cold air and is very efficient. In hot weather the Turbo will be less efficient and the engine has to work harder. Adding the higher octane fuel probably counteracts some of the power loss from the hotter air in the intake.

Anecdotally I have tried both regular and premium and have seen zero difference in fuel mileage or performance so far this winter.
The quick and easy reason for this is the cooler air will cause less chance of pre-detonation in normal driving. So, the lower flash point of 87 will still be enough octane to avoid this situation. As the temps warm up, the delta for air entering the combustion chamber increases, and brings the 87 octane closer to it's thermal threshold for detonation prior to spark.
 

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Crusifix

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Unless Jeep tells me to start putting E85 in the hurricane I'll stick to regular old fuel that is only subsidizing the corn industry at 10% or less :)

I think that recent corn news has me soured to it all :)

Yes. Please don't put E85 in your tank unless you are tuned for it. You will need a complete different injector cycle and PW. As well as spark timing. A quick for instance. I gained 37hp and 48tq in my mustang with E85 over 93 octane. This was naturally asperated. So, no turbo or supercharger. I know this, as I own my own dynojet.
 

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Can someone help me understand the mindset of someone who buys a new Wrangler for tens and tens of thousands of dollars, and I assume selects the 2.0 for the power characteristics to ultimately run a lower octane gas that FCA states will get optimal performance on premium? If you read their statement, it will always achieve optimal performance on premium fuel.
 

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I have 10k miles and a calculated average of 21.1 mpg of daily city/highway use on 93 octane. (computer says 23 - never trust it!)
Last week I hit 24 mpg for the first time!
I will start using 87 and see were it goes, at least until the HOT Texas weather hits...
 

WXman

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You purchased a Jeep for fuel economy? I have had cars that would pass anything but a gas station and demanded premium. Take your fun and pay for it
I read his post a few times, and I fail to see where he suggested any type of expectation regarding fuel economy. He was simply posting an update to the owners manual.

I'm a rebel. I run 93 in mine. What is another $4.00 per fill up over 87? If we could run e85 in these ...I'd be in true love. My choices are 87; 89 and 93 in my area.
Same here. I've never seen 91 octane at a gas pump anywhere in this part of the country. It must be a western thing.

I'm no expert but I thought that the jury had come back on Ethanol and it was no bueno for engines over the long run.
Ethanol is extremely corrosive. Even in today's vehicles, you do not want to let the vehicle sit for long periods of time with ethanol in the system. In addition to that, if the weather drops below about 40°F you can experience hard starting conditions. I've had that happen before myself. Ethanol isn't a good idea in cold climates. And like somebody said, E85 requires different fuel injectors and pumps and a proper ECU calibration to run safely.
 

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Yes. Please don't put E85 in your tank unless you are tuned for it. You will need a complete different injector cycle and PW. As well as spark timing. A quick for instance. I gained 37hp and 48tq in my mustang with E85 over 93 octane. This was naturally asperated. So, no turbo or supercharger. I know this, as I own my own dynojet.
Who was your tuner for your Mustang? I use to use Sean at AED for some of my tunes. I was never super happy with his tunes.
 

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Crusifix

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Who was your tuner for your Mustang? I use to use Sean at AED for some of my tunes. I was never super happy with his tunes.
I used Dakota at Lund for my 2014 GT500 and my 2016 GT. The guy is a master.
 

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I drove 600 miles home after buying my JLR 2.0L. First tank was 87 octane second was 93 octane. I got 19.7 mpg on 87 and 23.8 mpg on 93. Driving conditions were the same on both tanks. Engine felt much stronger running the higher octane.
 

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Been using 93 in mine but noticed the colder it gets (anything sub mid 30s F) she doesn't run as well as when we're in the 50+.
 

rommel102

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I drove 600 miles home after buying my JLR 2.0L. First tank was 87 octane second was 93 octane. I got 19.7 mpg on 87 and 23.8 mpg on 93. Driving conditions were the same on both tanks. Engine felt much stronger running the higher octane.
2 questions.

What is the weather where you are located?

What was your average speed?
 

rogo66

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2 questions.

What is the weather where you are located?

What was your average speed?
I picked up my Jeep late December in North Carolina. The temps were in the upper 30s lower 40s for the drive home.

It was a mix of interstate, highway, and city driving. On the interstate I kept it around 75. I did notice that it would shift to a lower gear on inclines much more on the 87 octane tank.

From my experience the engine just felt much happier with the higher octane.
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