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Unread 05-12-2012, 10:46 AM   #1
xlTravislx
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Switching gas types?

Ever since Ive owned my jeep ive put regular gas in it.

I was wondering if its bad for the engine or anything in general to switch from regular to premium every few fill ups, or even every other fill up?

Every time I go wheeling or on long trips Im tempted to fill up with premium for the benefits, But I don't want to spend the extra money every time i fill up for premium.

Thanks JF!

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Unread 05-12-2012, 11:17 AM   #2
cyberpyrot
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Ever wonder why you only see one gas truck at the gas station? Maybe the gas truck has 3 compartments.. Hmmm its a conspericy i tell you.
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Unread 05-12-2012, 11:40 AM   #3
2jhanna
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I am not sure you will see any benefits, but it shouldn't hurt anything.
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Unread 05-12-2012, 11:55 AM   #4
NonRubicon
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Won't hurt your engine, but it could hurt your wallet.

Unless you are getting engine ping, there is no reason to put in higher octane fuel. Premium fuel is for higher compression engines or engines that need higher octane to prevent detonation, and the additional cost is because of the octane enhancer that gets put into premium fuel. The other additives are the same, and usually in the same quantities as the lower octane fuels.

There could be benefit from switching brands, as companies have proprietary additive blends that differ.
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Unread 05-12-2012, 12:17 PM   #5
JohnnyWhitehead
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Quote:
Originally Posted by NonRubicon
Won't hurt your engine, but it could hurt your wallet.

Unless you are getting engine ping, there is no reason to put in higher octane fuel. Premium fuel is for higher compression engines or engines that need higher octane to prevent detonation, and the additional cost is because of the octane enhancer that gets put into premium fuel. The other additives are the same, and usually in the same quantities as the lower octane fuels.

There could be benefit from switching brands, as companies have proprietary additive blends that differ.
What he said. There is no benefit from running a higher octane fuel than what is needed. Actually it is just the opposite. It is harder for your engine to burn the fuel properly. Dyno test have proved time and again that running the lowest octane fuel your engine can without pre-ignition (knock) produces higher horsepower and torque ratings. Your 4.0 has a low compression ratio and will run better and more efficiently with 87 octane.

Now, if you can find ethanol free fuel that will benefit your engine and you will see an increase in MPG as well.
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Unread 05-12-2012, 09:14 PM   #6
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Higher octane fuels give off the best power at higher compression ratios. A stock compression ratio engine is not going to benefit from a higher octane rated gasoline.
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Unread 05-13-2012, 04:08 AM   #7
fmdualexhaust
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Quote:
Originally Posted by cyberpyrot View Post
Ever wonder why you only see one gas truck at the gas station? Maybe the gas truck has 3 compartments.. Hmmm its a conspericy i tell you.

Most tankers have 4 to 6 compartments.
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Unread 05-13-2012, 07:35 AM   #8
4x4jkx
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Higher octane gas prevents engine knock in higher compression engines. It prevents the gasoline from detonating due to compression caused by the upstroke of the piston (see: flash point). There is absolutely no benefit to adding this to your Jeep unless it is required to prevent engine knock.

Source: Thermo-Fluids Design Lab.
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Unread 05-13-2012, 07:55 AM   #9
FZY1
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I wonder if we can run E85 in our JEEPs 4cyl's and 6?
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Unread 05-13-2012, 09:21 AM   #10
Xpress
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Our engines weren't really designed to run on E85, it's a higher octane fuel as well (103). Flex fuel vehicles often average LOWER fuel economy on E85 than they do on gasoline (very likely because the engines were converted to run on E85, rather than desgined to).

If you utilize an engine designed for E85 (you would need a higher compression ratio, something like 14:1) then you would absolutely see the benefits.
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Unread 05-13-2012, 10:23 AM   #11
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Quote:
Originally Posted by Xpress
Our engines weren't really designed to run on E85, it's a higher octane fuel as well (103). Flex fuel vehicles often average LOWER fuel economy on E85 than they do on gasoline (very likely because the engines were converted to run on E85, rather than desgined to).

If you utilize an engine designed for E85 (you would need a higher compression ratio, something like 14:1) then you would absolutely see the benefits.
They get less mpg on e85 because there is just less energy in e85. And surprisingly a lot if cars were designed in mind for e85. Since the 90's.
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Unread 05-13-2012, 10:39 AM   #12
Vin
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I've run premium for half a year then regular for the rest just to see the difference. I found very little difference.
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Unread 05-13-2012, 12:55 PM   #13
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Although not the same engine, 4.2, I had switched from regular gas to premium to see what would happen with my CJ and I was pleasantly surprised at the results. The gas cost more but the mileage I gained made it so worth it. Now that was many years ago and gas was sooo much less than it is today of course.
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Unread 05-13-2012, 06:59 PM   #14
xlTravislx
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Thanks for the help everyone.

I might try it out for a few months to get my own opinion. As long as it wont do damage. This has been on my mind for the past year.
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Unread 05-13-2012, 10:48 PM   #15
Brainwashed2566
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I filled up with premium before a trip on accident (about 15 gallons premium to 4 gallons regular). Didn't really notice any difference. Any who here is what the 05 service manual says about premium/ and fuel blends.



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