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differnce in running premium fuel


brdhntr
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who has had gas mileage improvements with premium gas? i have but it's better to run the cheap stuff with ethanol here in the winter. it keeps things from freezing up at -27.

 

my audi, even in winter, has never seen a drop of anything but premium fuel. for 12 years it was nothing but amoco premium as well. nothing with any extra additives tha can harm o rings or companies that just run whatever gas was cheapest at the substation that day. amoco used to have there own plants and substations. but that was a long time ago. i only put other brands in when i was on long trips and amoco wasn't available. things have changed alot now. i only run prmium on road trips. i got into premium back in the mid 80's when i was delivering pizza's in my beater honda. i tried it once and stuck with it when i figured out the mileage difference. so i know there is a difference but i've never checked on the manche to see what the difference really is. i've got an 87 2.5. just curious to hear from those who have figured it out.

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Depends on the vehicle, depends on the elevation, depends on the ambient air temperature, depends on ambient humidity.....

 

Basically, it depends.

 

You can't just make a blanket statement that running higher test fuel is gonna return higher fuel economy.

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You have to be careful,different engines react differently.

 

If you don't have the compression ratio to efficiently burn premium you could actually lose performance and fuel mileage.

But he has an '87. The '87 is a Renix, with a knock sensor. Running high test retards knock, which allows the computer to run the engine with more advance, more of the time.

 

When my '88 XJ was new, I ran it on high test. I got as high as 28 MPG on the highway with that setup. But the newer gasolines with ethanol won't do that, so I'm now back to running regular. On the newer Jeeps with the Chrysler computer, there's no knock sensor so you won't see much (if any) improvement from running a higher octane than what's needed to avoid ping.

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i wasn't looking for a blanket statemenat that it does best in all situations, just what others have noticed. i understand temp, humidity and sea level effects, as well as condition of the engine and tire pressures, as wel as modifications.

 

i haven't driven my jeep on the road enough playing with fuel yet, i've gotten 21.5 hiway running whatever through it, both ethanol and non-ethanol. i've noticed it runs better with non-ethanol (premium here), but not checked mileage. just wondering what others think. i know some have said only run non ethaonal as it effects performance and i would assume that includes gas mileage.

 

just curious.

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higher the octane more slower fuel burning. which why it making timing retard. i wouldnt use another octane different from recommend unless ecu got retune.

 

Higher octane allows more advance,its harder to ignite so its less likely to missfire or pre detonate.

 

That's why most cars with high compression or forced induction require premium

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higher the octane more slower fuel burning. which why it making timing retard. i wouldnt use another octane different from recommend unless ecu got retune.

 

Higher octane allows more advance,its harder to ignite so its less likely to missfire or pre detonate.

 

That's why most cars with high compression or forced induction require premium

I knew it lol I means advance*** my bad :oops:

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With Jeep motors it is two-fold. They like to run on pure gasoline, which premium is more of. On the other hand, it is very difficult to ignite the high test stuff in our low reving, low compression engines.

 

I have achieved my best mpg running 85 octane when I lived in Vail with my lifted TJ, 22 mpg everyday. At that time it would only pull 16mpg in KS. Also, when coming out of the Wyoming high country in my wifes Camry, full of 85, we managed 41mpg (typical is 32).

 

I ran premium (91) in my TJ once in the same configuration as it was when I was in Vail. 15mpg highway.

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So here is a more important question: Ethanol or No Ethanol?

 

I've noticed that the renix setups on both of my MJs like gas that is ethanol free...

 

 

 

here the only gas without ethanol is premium, the rest is 10% ethanol.

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